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Amazon Music Stream millions of songs. Amazon Advertising Find, attract, and engage customers. Amazon Drive Cloud storage from Amazon. Alexa Actionable Analytics for the Web. AmazonGlobal Ship Orders Internationally. To the east, in a steep road winding through the woods of Acton Scott, many exposures occur, and several Lower Silurian forms may be collected. Another path through the same woods, but in a S.
Starting again from the same station southward along a lane, within half a mile a large 23 quarry on the right hand side among the woods will repay a search. Lastly, the road to Cwm Head which leaves the station towards the west, leads within a couple of miles to Broken Stones, so called from the masses of rock which owe their irregular form to the faulting and contortion to which this district has beea subjected.
Here are foimd the Corston grits and the Longmynd strata, in close proximity. Higher up, where the river has undermined the bank, may be seen the purple beds or lowest layers of this formation, and still further on, the famous " Onny section," where the succession of Wenlock, Llandovery, which is however only represented by a few calcareous courses , and the upper beds of the Bala or Caradoc can be seen in their normal position.
Near the river, on both banks, many other exposures will be found, until at Horderley a large quarry displays a fine section of thick bedded purple and green sandstones, and abounds in a variety of characteristic forms. A quarry in a thick bed of limestone, which is a portion of the Corston grit bed, and, a little further on, a stratum of Cambrian sandstone resting conformably on the last named rock, will next demand attention; but the disarrangement which has here taken place in their relative position, makes the geology of the locality difficult to determine.
We next find exposures of the Wenlock Shale, underlaid on the south-eastern and western flanks of the Longmynd by the Mayhill Sandstone, and a well marked conglomerate Mayhill , which, with the Pentamerus limestone bed, is well exposed a short way up the hilL Thence, pursuing the road by the south of the range,.
Plowden station on the Bishop's Castle line is reached, beyond this, in a deep cutting, the grey and purple strata of the Wenlock are exposed, and the same may be traced in other spots in the neighbourhood. Before leaving this place a visit should be paid to a fine conglomerate of great thickness on the western slopes of the Longmynd, probably of the same age as that which has been noticed at Sharpstones and Lyth Hill, near Shrewsbury.
Diverging from the route just described at Longville Common, the summit of Wartle Knowle can be reached. This, which is coloured in the geological maps as belonging to the Cambrian, is believed by Dr. Callaway to be a portion of the Precambrian, and is well worth a careful examination ; from this point Craven Arms can be reached by Long Lane, in which are good quarries of Horderley Sandstone.
A return can be made thence to Craven Arms by Grinnels Cross. Near the top of the road leading to this latter place, is an old quarry in which several good specimens have been found, among them the rare Gomphoceras Bohemicurtu d. One of the most instructive sections which the Geologist can explore may be examined by again leaving Craven Arms by the Corvedale road.
Within about half a mile, near Halford vicSirage, he passes over an outcrop of Wenltfck Limestone. Further on are large quarries of Aymestry Limestone well displaying its thickness and characteristics. Tummg to the right from the high road at Grinnels Cross, the Aymestry may again be noticed in a quarry on the right hand side. From this, the road leads to Norton farmhouse ; opposite to which, on the right, and up the lanes leading to Norton Camp at the summit of the hill, are good exposures of L'pper Ludlow, where some fine specimens of Homolonoius Knightii and several other fossils.
In a lane, behind a cottage to the south of the farmhouse, and but a few yards off the road, is to be found the finest exposure known of the Ludlow bone bed. It is here in some places six inches thick and forms at one spot the bed of the lane itself. About a yard above it there is a bed of shale abounding in Platyschisma and Modiolopsis Lcevis, It is remarkable that a bed in the same relative position exists at Ludlow and Downton Castle, where also the bone bed is found. A few yards further towards the east the Downton Sandstone may be detected overlying the above strata and conformable with them.
Leaving Norton, the road may be taken to Onibury, at a short distance from which the Transition beds, preserving the same characteristics as they present at Ludlow and the Tin Mills, will be seen in the side of the road which passes through them, and their relation to the old Red strata, also exposed here, can be clearly made out Fossils are not numerous, but specimens of Eurypterus have been procured.
Nearer Onibury is a large quarry of Downton Sandstone in which Lingula cornea and many carbonaceous fragments abound. About a quarter of a mile from Onibury on the road to Craven Arms is a large and prolific quarry of Upper Ludlow. A mile further on, a wooden as bridge across the Onny river leads into the meadows on the right bank. Passing under the railway arch, and proceeding northward, some limekilns are reached which. A little further on, overshadowed by some large elms, is a quarry rich in specimens belonging to the Lower Ludlow rock.
The visitor to this beautiful valley will do well to finish his day's ramble by exploring the fine fortified Edwardian mansion of Stokesay Castle. A divergence from the above route may be made at Stoke farm buildings to the summit of Weo or View Edge, where in some extensive quarries, the Aymestry limestone, which formg the crest of this as well as of the opposite hill of Norton Camp, is well displayed, and the characteristic fossils abound.
Taking the train from Craven Arms to Broome and leaving this station in a westerly direction, the Corston Grits will be found near a farm of that name on the side of Clunbury Hill, brought by feult into close proximity with the Ludlow Shales, of which a vast expanse lies to the west f, Within about two miles of Bucknell station, on the same line of railway, is Pedwardine, remarkable for its exposures of Shineton Shales.
Here the relative position of Mayhill or Llandovery Sandstone should be observed, as well as the quarries in Brampton Brian Park, where highly hiclined Cambrian grits, and Pre- cambrian rocks are found. These have in some instances been used by the pre-historic inhabitants of this district in the construction of the stone circles and dolmens of which the remains are still to be found. The best localities for fossils in this neighbourhood are — i, Radnor Wood, one mile east of Clun on the road to Craven Arms. Rock of Woolbury on Black Hill ; one and a half miles S.
All three belong to the Upper Ludlow formation. The Transition beds between the Ludlow and the old Red are also to be observed, but no fossils have as yet been discovered in them. Since Ludlow is situated close to the boundary of Shropshire, the river Teme separating it from Herefordshire, the explorations of the geologist in its neighbourhood must necessarily extend into the latter coimty.
We shall have therefore, in describing the following routes, to depart slightly from our original plan, and to carry our researches to a short distance over the limits of Shropshire. In the immediate vicinity of the town itself several good points of observation are afforded. In the beautiful walk below the Castle and in the road lower down, the Upper Ludlow rock has yielded several fine specimens of Homolonotus Knightii to the hammer of Mr.
Crossing Dinham Bridge, at the foot of Whitcliffe, there is a section of the uppermost beds of the Aymestry Limestone which abounds in fossils, some of them very rare. Not far from this quarry is Ludford Lane, distinguished as the locality in which the famous bone-bed was originally detected. The position of this interesting deposit in relation to the strata above and below it can here be very well studied.
In this stratum besides the curious Onchiu spines and fragments of fish defences, a variety of remains of the highest interest may be collected At the south end of the tunnel close to the Railway Station, the Passage or Transition beds between the Silurian and old Red formations were largely exposed during the construction of the railway, and yielded a rich collection of fossils, including two new Cephalaspidcty viz.
Ornatus and C Murchisoniiy Auchtnaspia SdUeri, Pterygotus, Eurypterusy Beyrichia, 4cc, 4cc, A good section displaying the same formation will, be found in the right bank of the river Teme, below the weir, about a quarter of a mile from Ludford Bridge. This is the only place in this stratum in which Mr.
Marston, that most industrious collector, has found organic remains, viz. Few excursions in this district will be found more instructive and enjoyable than the following. Leaving Ludlow by the Shrewsbury road, turn off at Bromfield to the left towards Leintwardine. Within a couple of miles the road winds up a hill over the lower strata of the Downton Sandstone, and passes by a large quarry of the Upper Ludlow on the left, and still further on, several exposures of the same: Here a very fine and interesting section is displayed.
The fact, however, that this stratum overlies the Aymestry seems to confirm the conclusion arrived at by Mr. Lightbody, and alluded to by Sir R. Murchison in his Siluria, that the Limestone properly belongs to the Lower and not the Upper Ludlow rock. Otherwise, it may appear that it cannot be considered as a boundary between the two, but only as a local calcareous deposit. We may now either descend the steeply inclined road to Leintwardine by Mock- tree, by which a magnificent section of the Aymestry and Lower Ludlow may be studied, or, better still, strike across a couple of fields by the top of this great quarry into an old road, on the right of which a quarry displays the same succession of Limestone and overlying Church Hill slaty shales, and in these Star Fish and Ceratiocarisy dr'r.
From this point we descend to Leintwardine and again diverging to the left, reach the far-famed Church-hill. These are however unfortunately filled up, and the supply has at present nearly ceased. From the summit of this hill an old lane leads to Trippleton farm, close to which is another good quarry replete with fossils. The road should then be pursued for about a mile to where another crosses it at right angles, and from this spot an excellent view is obtained of the Valley of Wigmore.
Ridges of Wenlock and Aymestry Limestone run round the great amphitheatre of which the centre has been hollowed out by denudation, leaving the Wenlock Shale exposed in the lower parts. Under the overhanging banks of the river which winds through this valley, excellent specimens of Phacops iongicaudatus and other characteristic forms may be collected. The road may now be taken either to Burrington, where the Wenlock Shale is well exposed, or back to Ludlow by Downton. On ascending the hill towards the latter place, a steep lane to the right leads down to the banks of the Teme, at the Bow Bridge.
Here is displayed a fine cliflF of Aymestry as well as exposures of Lower Ludlow prolific in good specimens. Lower down the river, near the Forge Bridge, in the road which has been deeply cut into the rock, on the left hand side as you descend, at the height of about six feet, the Bone bed already described may be examined.
In a hollow running up the hill to the right, about a quarter of a mile from the town, many good specimens from the Upper Ludlow have been found. Further on, Mary Knowle Dingle furnishes many exposures; and still further, at Batchcott, some extensive quarries are well worthy of a search. On reaching the Rectory of Richards Castle, the road should be taken up the hill to the right, and 28 soon the Church will be reached; passing which as well as the ruins of the old border fortress, we arrive at a beautiful spot known as the Bone Well; where a clear spring issues from among masses.
A pathway up the hill and over some undulating ground leads at last to the top of Evenhay Lane, descending which to Elton, and near the bottom of it, some capital fossiliferous exposures of Lower Ludlow will be found. Several good exposures of Aymestry limestone and of Ludlow rock will be observed on the way, in one of which the peculiar spheroidal structiure which is sometimes found in these rocks, is well displayed.
The wild and secluded district north of the Tittestone Clee Hill may be best reached from Ludlow by way of Cleobury Mortimer. N entering upon this portion of our work, we would call attention to the remarkable changes which have taken place from time to time in the prevailing forms of animal life. While a few genera, such as Lingula, have been strikingly persistent from the earliest period of which we have any record down to the present day, the duration of others has been confined within more narrow limits.
Again, the bivalve Brachicfiods, which swanned in the Silurian seas, have ever since been gradually disappearing, though they are not yet extinct ; while the more highly organised Lamellihranchs Pelecypoda , of which there were but few types in Paloezoic times, have been continually on the increase. Once more, the CvUh fiahea Octopoda , the ISavAUM Telrabraruhiaia , and a very few other forms, are the sole descendants of a numerous and often gigantic race of Cephahpodt of the primxval ocean. These organic changes, as well as the tendency which may be observed throughout all time to replace lower by higher types, have an important bearing upon one of the most interesting questions of our day, viz.
The classification of organic beings, to be accurate and complete, should be based on a knowledge of their development and growth, as well as of their internal and external stmcture. Of these conditions the last alone is, fur the most part, available to the naturalist in assigning to fossils their proper place in the scale of organised creatures: There are, however, certain broad lines of distinction which it will be possible to draw ; And we 30 therefore propose in the following sketch to describe a few of the main features by which the great families and genera of extinct animal life appear to have been con- nected with those of the present day, and wherein they differ from them and from each other, and thus to render some assistance to the student in arranging his collec- tions.
Those who desire to enter more deeply into the organisation and classification of palseozoic remains should consult Nicholson's " Manual of Palaeontology," Wood- ward's " Recent and Fossil Shells," LyelFs " Student's Elements of Geology," S-c. The following are the chief divisions of the animal kingdom: The animals included in this division are generally of minute size, and, for the most part, are composed of a structureless jelly-like substance, and possess no definite nervous or digestive apparatus. They are represented in the present day by several orders among the Foraminifera and the Protean animalcules such as the Amceba, The only genus with which we are concerned which can with probability be referred here is that of Sirotnatopora PL viL fig.
This fossil is found in the Silurian and Devonian rocks in masses of varying shape and size, and sometimes grows para- sitically on shells and corals. Its essential features are concentric laminae separated by interspaces, sub-divided by vertical pillars or partitions. The whole mass of the fossil is penetrated by pores and canals, and the surface often exhibits conical elevations or papillae. It is probably allied to the sponges. The curious fossil Ischadites Kanigii PL xvii, fig.
Animals whose alimentary canal communicates freely with the general cavity of the body. Most of them are furnished with tentacles, and the organs of the body present a radiate appearance. The surface is studded with blunt spines which, in vertical sections, are seen to be the summits of pillars ; the spaces between these are occupied by calcareous plates ; it is free from apertures, and the animal was attached at one point only to the substance over which it grew. Animal compound and plant- like, consisting of numerous polypites protected in small cup-shaped expansions on the branches, called hydrotheecB.
The last named superficially resembles FeneaUlla which belongs to the Polyzoa , but the latter hare a calcareous skeleton and possess no cellules. They are known by their toothed or serrated appearance and resemble the living SerttUariaru in some respects, but differ from them m having been apparently unattached and in possessing a solid axis which is never present in the latter. The general homy covering of the GraptolUes extended over the hydrothecae or cup-like projections in which the polyp dwelt. There is reason to suppose that the axis whicli connects the hydrothecs was not solid but was filled with living material.
It is generally extended beyond one, and, in some genera, beyond both ends of the polypary. The cellules are separated from each other by partitions, but communicate by canals, and each opens at its apex by a distinct mouth through which the polypite extended its tentaculite head. Two predominant forms may be noticed in this sub-class. Class B — Actinozoa. Stomach opening into the body cavity and not identical with it, as in the last class.
Genus r , — FavosUes, PL viii, fig. Nearly allied to the same genus is Ccenitea PL vii, figs. These corals, similar to the last in the absence of septa and the possession of tabulse, are distinguished from them in the fact that the walls of the corallites are without pores. The corallum itself assumes various forms, being sometimes massive, or branched, or laminar, or encrust- ing, and the corallites are of small size. Septa rudimentary ; tabulae well developed. Genus 1, — Halysites or the chain coral PI. The long tubular corallites are united in lines so as to form vertical plates having interstices between them.
The septa are 1 2 in number and are close to the walls. Genus 2 , — Syringopora, PL vii, figs. Allied to Halysites, but the "Corallum is fasciculate, the corallites cylindrical, long, and united by hollow, tubular, horizontal, connecting processes ; so that though the wall is imperforate the visceral chambers of contiguous corallites are placed in communication. The systematic position of the section is however doubtful.
This order includes a very large proportion of fossil corals and seems to have disappeared, with one exception, with the Palaeozoic epoch. Its chief characteristics are ist, that the septa generally consist of four and multiples of four, whereas those of modem corals included in the order ZoarUharicty in other respects resembling these, consist chiefly of six and multiples of six. Tabulae are always present. To this group may possibly belong the genus Fttroia, PL v, fig. Corallum may be simple or compound ; septa more or less radiate ; fossula generally absent ; tabulae confined to the central area.
Genus 2 , — Omphyma, PL viii, fig. The septa are divided into four groups by shallow depressions or fossulse, and the corallum was attached by root-like projections from its base or outer wall.
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Strombodea differs from Acervularia in possessing funnel shaped tabulae. The corallum is usually simple but occasionally compound. The septa are rudimentary and appear as striae or ridges within the calyx or cup of the coraL The mass of the coral is composed of cellular or lenticular-shaped bodies.
Corals composed of tubes of two sizes, the larger of which alone have rudimentary septa but both possessed tabulae; coenenchyma abundant. In the modem representatives of this family the polyps possess eight tentacles. Among their representatives in the Palaeozoic era are the Aateroidea or Star fishes. The body of these is pentagonal and consists of a central disc in which is situated the mouth. The arms, of which there are generally five, are hollow, and contain prolongations of the stomach ; they are grooved underneath, and from the grooves the tube-like feet protrude in two rows.
Owing to the imperfect state in which the more perishable portions of fussil star fishes are preserved, it is difllicult to assign their position among known genera. This genus comprised some species of considerable size. Genus 2 , — Palasierina, PI. Disc much enlarged, and the plates which surround the mouth large and triangular. The arms are not grooved beneath for the insertion of tube-feet, and the mouth appears to have been furnished with a masticatory apparatus.
The Crinoids or sea lilies were fixed to the sea bottom by means of a stalk of varying length, jointed and flexible. The head is cup shaped, and furnished generally. From it rises a proboscis-shaped tube, which is sometimes of great length, and which is supposed to be anal in its functions. It having, however, been observed that the shell must have been long attached to the proboscis, since its lip has become worn to the shape of its surface, it is more probable that the mollusc attached itself to the crinoid for the purpose of feeding on the excreted fragments of the animalculse which formed the food of the latter.
The arms which spring from the margin of the calyx are united to it by plates, the number and character of which are of importance in classification. Basals five, alternating with five parabasals ; the arms generally have three radials. Genus j , — Taxacrinus. Parabasals five, large, succeeded by from three to seven radials in each arm. The parabasals are absent. The cup consists of three basals, which each support two sets of radial plates of which the primary ones are much the largest The secondary radials bear bifurcated arms and these are fringed with pinnulse or filaments.
The calyx is deeply concave at the base like the bottom of a wine bottle. It has four small basals which cany five large primary radials, these are succeeded by others, and the last are developed into long club-shaped processes which lie in grooves formed by the sides of the calyx. The type presented by this last genus is in many respects very unlike that of the preceding. Resembling the Crinoids in the possession of poly- gonal calcareous plates, but differing in the absence of arms, since the jointed processes which are attached to some of them bear a closer resemblance to the pinnulse or lateral branches of the Crinoids.
The Cystoids are confined to the Cambrian, Silurian, and Devonian eras. The functions of the curious cells and apertures seen in some of the plates with which they were covered, are little understood. We shall only briefly indicate the chief characteristics of some of those which are figured. Five grooves on the surface which appear to correspond with arms bordered on each side by a row of short pinnulae. The body is oblong and tetragonal. Animals whose bodies are composed of a number of segments arranged one behind the other. The calcareous tube in which the animal lived and into which it had the power of retreating, sometimes attained the length of three or four inches.
It is marked by a number of rings, finely striated. This form has survived to the present day and is found attached as a parasite to other shells. The fossils figured are supposed to be the casts of the membranous tubes occupied by the worms. Atiimal not con6ned to a tube. The only traces kiiowti of them are their fossilised tubes, burrows, and the trails which they made on the mud and sand as they glided over it ; and thus a creature as perishable and fragile as the ordinary earthworm has left behind it a record of its existence older than any other known fossil.
In the first, the depressions occur in pairs, atld are caused by the fact that the anelid formed U-shaped bufrows in the sandy or muddy shore of the period, of which these small depressions are the summits. A common fossil in the Upper Ludlow rocks, which sometimes attained a great length, belongs to this group. They are divided into the following four classes, of which we shall have occasion to notice only the first.
The Crustacea have been divided into several sub-classes and orders; the following include the fossils with which we are concerned. Body enclosed in two unequal calcareous bean shaped valves. Near the hinge there is a small tubercular eye-spot, and the shell exhibits reticulated markings, and a groove extending a short way across the valves.
Genus 2 , — Primitia. Carapace equivalve, convex, oblong, with a dorsal groove of variable length. Related to the last, but characterised by two or three transverse grooves passing from the hinge across the valves. Genus r , — Hymenocaris, The carapace or shield, which covers the fore part of the body, is not apparently bivalved and is sott;ewhat triangular. There are nine segments of the body and the last bears three spiked appendages or sets. Gill-like plates connected with the under surface of the caudal segments have been detected in some specimens. In describing this important order of Crustacea we refer for the explanation of the terms employed to PI.
As the name implies, the animals included in it present a more or less trilobed appearance. The body may be divided into three well marked divisions: The head, or cephalic shield, is composed of three pieces variously united together. The central one is called the ''glabella," and varies much in form.
It is bounded by two "axal" grooves, posteriorly by a third groove "the neck furrow" and is generally lobed transversely. It is probable that these lobes corresponded with certain appendages beneath, jaw-feet, pincers, Ac , of which no trace has as yet been found. The free cheeks terminate behind in angles, "genal angles," which are sometimes prolonged so as to form spines, and they also support the eyes, which when present are usually compound.
The number of lenses of which they are composed is very variable, there being in some genera as few as 14, and in others as many as 15, The body rings, which are movable on each other, constitute the thorax. Their trilobation is generally well marked. The central lidge is called " the axis," and this is separated from those on each side, "the pleurae," by a groove, "the axal furrow. Lastly, the tail or "pygidium" consists of a central lobe or axis and two lateral portions called " limbs.
But little is known of the under surface of trilobites. The head was furnished with two plates beneath, the anterior ca'led the " rostral shield," and the posterior the " labrum. The ova of trilobites have been observed: The only living creature which appears to represent this family, so important in the Silurian era, is the Limulus or king crab. This, in its larval condition, presents distinct traces of trilobation and bears a strong resemblance to Trinucleus.
The head is large and the cheek angles produced into outwardly bent spines. The glabella has lateral grooves and the sutures unite in front of it Eyes long and reticulated, enclosing the glabella. Eleven body rings, the seventh with appendages on the pleurae. Tail very small and sometimes with but two segments. Glabella contracted in front.
This, as well as the preceding family, is only found in the Cambrian strata. It has some resemblance to Calymene. Glabella wide behind and contracted in front ; facial sutures discontinuous. The fixed larger than the free cheeks, fourteen or fifteen facetted body rings Tail has from two to eight segments with entire margin. Phacapa, PL x, fig. The glabella very broad in front and with three lateral grooves.
The facial suture cuts the external margin of the cheek. Eyes conspicuous, facetted, and reniform. Pygidium with from eight to fifteen segments. In both the glabella is widest behind and the facial sutures between the posterior and exterior margin. Eyes minute in the middle of the cheek, reniform and facetted. Ilomolonotua resembles Calymene in many respects, but the trilobation is much more imperfect and it is distinguished by the broad, highly convex thorax. Facial sutures not continuous.
Eight or ten body rings, grooved. Three pairs of lateral furrows. Pygidium, four to thirteen segments. Genua 2 , — Cyphaapia, Differs from the last in having a more convex glabella, ovoid, smooth, and remote eyes, gibbous cheeks, and eleven to seventeen body rings. The sixth segment bears a spine. The general form like Proetua but body rings from nine to eleven. The tail semi-oval with entire margin ; segments eleven to sixteen.
Eyes large and reniform. Head very convex, semicircular. Central lobe of the glabella grooved behind. Eyes smooth and reniform. Thorax of eleven segments, with grooved, flat, falcate pleurae ; pygidium semi- oval; axis undefined, larger than the head, often spinose. Contains but one genus, Acidaapia. The head is short, broad, truncated in front, and marked by a second pair of axal furrows. Thorax has nine or ten segments, with a narrow, convex axis and horizontal pleurae terminated by spines.
Tail small and fringed with spines. Facial sutures continuous, ending on the posterior margin. The general characteristics of this family are the great size of the head and its wide margin. Glabella conspicuous, pyriform, convex. Body rings five or six, with grooved pleurae ; axis convex. Lateral grooves and facial sutures obscure.
A small tubercle, possibly an eye, is sometimes found on the lateral lobes. Tail triangular ; edge elevated. Glabella prolonged into a beak and long spine. Margin of shield not perforated as in Trinticleus. Facial sutures absent Five or six body rings. Large Trilobites of oval form and never tubercled or spinous. Facial sutures terminating between the margin of the shield and the axis. Body rings usually eight, with grooved pleurae. General trilobation comparatively faint Caudal shield at least equal to the head in size. I I ' 40 Labrum deeply forked.
Tail with entire, rounded margin, and sometimes nearly without an axis ; segments twelve to fourteen. Generally similar in form to the last, but axis of tail is more conspicuous. Glabella clavate, and distinctly furrowed transversely. The labrum is rounded and not cleft.
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Head and pygidium large and convex. Axis in both very obscure. Axal furrows of thorax distinct, the axis itself moderately wide ; eyes smooth, remote, and lunate ; glabella obscure ; rostral shield shuttle-shaped ; body rings eight to ten. Segments of the thorax five or six. Both head and tail large, and in the latter the axis is truncated. Glabella not well defined.
Facial sutures ending on posterior margin, close to the axis. Head strongly trilobed, semicircular, with rounded or pointed genal angles and arched glabella, which is deeply furrowed with three lateral grooves forming three lobes. Body rings generally eleven, with slightly grooved pleurae. Four distinct rings in the axis of tail, the pleurae of which are terminated by spines or points. Similar to Cheirurus in number of body rings and tail, but distinguished by the great inflation of the glabella, the facial suture ending on the external margin, and by having only three segments in the tail.
Glabella pear-shaped, with many tubercles. Lateral furrows very indistinct. Body rings eleven; on the 7th and nth occasionally spines. Segments of the tail numerous ; axis tubercular. Three lateral furrows in glabella. Segments of thorax only two, with grooved pleurae. Eyes and facial sutures absent ; the tail segment bears a small tubercle.
These remarkable crustaceans were furnished with a head shield, bearing a pair of larval eyes near the centre, and a pair of large marginal or suDcentral eyes besides. Behind the head were thirteen free segments counting the tail, without appendages. A plate or " operculum " was situated over the first two which probably protected the generative organs. There is every reason to believe that the berry-like bodies, which are found in strata where the remains of these crustaceans abound, described as Parka decipiens PI.
The Sub-Order Eurypterida is divided into four genera, viz. It made its appearance only at the close of the Silurian epoch. The animals included imder this head differ widely in their external form, but resemble each other in possessing soft bodies, in which the alimentary canal never communicates with the general cavity of the body. Although some of them, like the Cuttle-fish, possess an internal skeleton, this is never vertebrate ; and though many are protected by shells and other external calcareous structures, like the Polyzoa, these are not arranged in segments.
A nervous system of one, two, or three pairs of ganglia, sometimes a heart, and respiratory organs are present The Mollusca are divided into two great groups. In both, a large number of individuals are combined to form a com- pound coralline structure ; but in this respect the two are essentially distinct, that, whereas in the Sub-kingdom CoslerUerata, the cells of the separate polypites com- municate with the general cavity of the body, each individual in this class consists of a sac having apertures, one for the extrusion of the tentacles which surrounded the mouth of the animal, and one for the anus ; the alimentary canal connects these, and floats in the fluid which fills the sac, without opening into it We shall now describe a few of those forms which appear to be analogous to living structures, and have been named accordingly.
The calcareous structure which connects the polyp cells, and which is called the " coenoecium " forms a fan-shaped expansion attached by its base to some object It is composed of a number of parallel stems united by crossbars or ''dissepiments. Instead of crossbars the branches are united so as to form oval interspaces between them. The branches are not keeled, and have from one to five rows of cells, and the dissepiments are solid. Stems not united by dissepiments. One side striated, the other exhibits cell mouths placed alternately. There are also cell mouths in the side shoots of the fronds.
This genus represents a consider- able group of the Polyzoa. The margin of the frond is striated longitudinally and is destitute of cell mouths.
The genera Chastetea PL vii, fig. The invertebrates composing this class are mantle breathing bivalves, inhabitants of the sea, and are possessed of labial appendages, erroneously termed arms, and incorrectly supposed to be analogous to the foot of the Gasteropod, but through habit the name has been generally admitted.
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Moreover the two valves of the Brachiopod are sometimes slightly unequal to each other, and generally very much so, but are symmetrical, that is to say, a straight line drawn from the beak ta the centre of the margin would divide them into two equal halves. Those of the Lamellibranch are equal but not symmetrical They are often, from their resemblance to antique lamps, called " lamp shells. Generally the ventral valve ends in a " beak " which is perforated by a hole called the " foramen ;" through this passed a muscular cord or "peduncle," by which the shell was attached to marine objects ; when it is absent, the peduncle passed between the beaks of the valves, as in Lingula, or the shell was attached to the rock by its surface, as in Crania.
The shells are opened by the action of two muscles, of which one extremity of each was attached to a projection in the dorsal valve, the "cardinal process," and the other on each side of the centre of the ventral valve. They were closed by "adductor muscles" usually four in number. These have left scars at the places where they were attached to the shells, and which are of importance in classification.
A space, some- times considerable, between the beaks of the valves PL xiii, fig. In most cases also, it is perforated by a number of pores or canals, and is then called " punctate. These fleshy appendages are, more or less, supported by a calcareous process, varying in shape and extent in diflerent families and genera.
They are in some forms capable of movement The Brachiopoda are divided into two great groups: Those in which the valves are articulated by means of teeth and sockets. Those in which the valves are free. Arms supported by variously shaped calcified lamellae in the form of loops ; beak perforated by a circular foramen. Arms supported by a long thin shelly process, spirally coiled: Spirals differently directed in different genera, and usually connected by a more or less complicated system of lamellae.
Shells usually more or less trans- versely oval or elongated, hinge-line long and straight. Hinge area well defined and divided by a triangular fissure, partly arched over by a pseudo-deltidium. Bases of spirals facing each other, apices having a more or less upward direction towards the posterior angles of the lateral margins of the shells. Similar in shape to Spirifera but valves very imequal, ventral valve deep and conical, hinge area very large, foramen narrow arched over by a long narrow deltidium, perforated, up to a certain age, by a circular foramen.
Spirals as in Spirifera. Genua 3 , — Athyria, PL xiii, fig. Shell biconvex, more or less circular, beak incurved, perforated by a small foramea Spiral supports large, facing each other in the centre of the shell, apices directed towards the lateral margins of the shell, spirals connected by a complicated system of lamellae. Spirals as in Athyria but differently connected. Spirals oval, direction as in Athyris.
Loop connectmg spirals, Y shaped, with sharp angular extremity, sometimes prolonged into a spine-like process. Genua 7 , — Atrypa, PL vi, fig. More or less circular. Bases of spirals conical, directly facing the bottom of dorsal valve. Loop, connecting spirals, simple. Beak pointed, much incurved. Arms spirally coiled as in Atrypa, attached at their base to short curved processes. Valves more or less unequally conyex, dorsal valve elevated in firont ; foramen under the beak, and entirely completed by a deltidium. CardinaT process in dorsal valve large and bifid.
Shell more or less triangularly ovate. Dental plates converging, trough like, supported on a prominent septum. Dorsal valve with two contiguous longitu-' dinal septa. Genua S , — Stricklcmdinia. Shell oval, but valves not disproportionally imequal; a short mesial septum in the interior of ventral valve supporting a small triangular chamber beneath the beak.
In dorsal valve two short hinge plates with two calcified processes for support of arms. Hinge line generally shorter than the width of the shelL Valves semicircular, generally biconvex, area in both.
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Surface smooth, ribbed or striated. Shell semicircular, widest at the hinge line, one valve convex, the other concave ; surface rarely smooth, generally striated. Hinge area double, with a triangular fissure in the ventral valve, arched over by a deltidium. Beak in the young of some species showing a small circular foramen. No processes for the attachment of the arms. Englypha PL xiii, fig. Genua 3 , — Leptama. Very similar to the last, but may be distinguished by the long hinge line, the very curved shells, and the long muscular impressions.
The dorsal valve is concave. No calcified supports for the arms, hinge line straight, ventral valve convex, dorsal concave ; rarely articulated with teeth. External surface studded with tubular spines. Hinge line as wide as the shelL Both valves have a hinge area, with central fissure, which in the ventral valve is covered by a deltidium ; its hmge margin is also furnished with a row of spines. Valves without teeth or sockets, transversely elongated and occasionally furnished with ear-like expansions. Shell attached to submarine substances by the whole or. Umbo or apex of dorsal valve, sub-central, or marginal Family VII.
Shell attached by a peduncle passiiig through the ventral valve. Upper valve limpet shaped, smooth or concentrically stnated ; lower valve flat or slightly convex, perforated with a slit situated in a depression of the surface. Ventral valve has a slit at the margin. Surface radiately striated and pitted. The beak of the ventral valve hais a foramen which communicates with the interior by a tube. Surface concentrically ridged, and covered with delicate spines.
Texture homy, arms fleshy. Dorsal valve a little shorter than the ventral. Shells tapering towards the beaks. Diflers from the preceeding in having a groove for the passage of the peduncle. The ventral valve has a furrow for the passage of the peduncle. Billings as diflering firom the genus Obolus in having the smaller extremities of the two central muscular scars directed upwards, and diverging firom each other, whereas in Obolus the arrange- ment is exactly the reverse. Davidson expresses himself with reserve about this distinction. Molluscs included in this class have been so named from their possessing two lamellar gills or branchiae on each side of the body.
The animal is enclosed in a shell composed of two valves, generally united by teeth and sockets, but sometimes by a ligament The shells of the Lamellibranchs in general are different from those of the Brachiopods in not being, as the latter always are, equilateral ; but being, unlike the Brachiopods, mostly equivalve. We shall therefore only indicate those external characteristics which afford the means of classifying them.
The following definition of the terms used will help to shorten and render clearer our description. Each valve is essentially a hollow cone of which the apex is turned more or less to one side. The length of the shell is measured from its anterior to its posterior margin, and its breadth from the dorsal side to the base. Some Lamellibranchs possess what are called respiratory siphons, others are destitute of these organs ; and the dass is accordingly divided into two sections: Shell inequivalve, oblique ; umbones anterior, eared, the posterior ear wing-like ; hinge with obscure teeth or none.
Genut 1 , — AvieultL PL xviii, fig. Shell very oblique and inequivalve. The hinge has one or two small cardinal teeth. It is doubtful whether many of the Paleozoic shells which have been referred to this family, properly belong to it. Shell obUque with nearly equal convex valves. Winged posteriorly ; anterior ear nearly absent Surface ribbed.
Shell oblique and equivalve with prominent beaks. Surface with radiating ribs. Hinge area short and flat The affinity of this shell is doubtfuL Genua 4. Shell resembling Avicula, but nearly equivalve ; there are a few anterior radiating teeth, and elongated, oblique, posterior teeth on the long, straight hinge line. Shell very inequilateraL Surface smooth, marked by concentric lines. Posterior end of shell much broader than anterior. The ligament which united the valves has left a groove beginning in firont of the beak and extending to the posterior extremity.
Shell elongated, equivalve but very inequilateraL Beaks close to the anterior end. Margins of shell parallel. Hinge long, with many teeth. Shell trigonaL Beaks reversed, t. Hinge with numerous teeth. Affinity of Palaeozoic Nucuke doubtful. Posterior side usually shortest. There is a strong rib behind the anterior adductor impression. Shell equivalve, heart-shaped with radiatmg ribs. Cardinal teeth two, lateral teeth one in each valve. Shell very oblique, keeled.
Anterior end short and truncated. Hinge tine long and straight Two cardinal teeth with a hinder lateral one.
Shell equivalve; ligament external Cardinal teeth one to diree in each valve, and usually a posterior tooth. SheU trapezoidal, ladiately striated. Hinge with three radiating cardinal teeth. Shell often inequivalve, with external ligament. A single or double fold extends from the beak to the middle of the ventral margin.
Their univalve shell is not, like that of the Cephalopod, divided by septa into chambers. A muscular foot or disc, of which that of the snail is a familiar example, is formed by the ventral surface of the body and furnishes the means of locomotion. A univalve shell may be described as a more or less elongated cone. That of the Limpet is an example of its simplest form. But it is usually prolonged into a tube, the mollusc being attached to and coiled round a central axis, " the columella. In this case the shell is said to be " discoidal: Through this notch the syphons pass which convey the water to and from the gills for the purpose of aerating the blood Those gasteropoda of which their shell-apertures are entire are generally vegetable feeders, while those in which they are notched are carnivorous in their habits.
The former were most numerous in Paleozoic times. Shell long and spiral turreted , whorls convex, without spiral band. Surface covered with longitudinal sinuous lines or striae. Shell tubular or spiraL Aperture simple. The genus HdopeUa PL xiv, fig. Shell of few whorls, conical, smooth. Whorls convex, base rounded. Apertures large and rounded. Palaeozoic form of doubtful afiUnity.
Shell depressed or discoidal. Whorls angulated, and aperture polygonal Umbilicus large. BaphiatamOf PL v, fig. Base flat Shell pyramidal. PiatyschismOy PL xviii, fig. Shell spiral or pyramidal. Genus 1 , — Pleurotomaria. Shell very variable in shape ; in some cases resem- bling Trochua, in others Turbo, or much flattened or depressed. Whorls few, occasionally the last disconnected from the others. Aperture, sub-quadrate, dis- tinguished by a slit in the outer lip which, as the shell grew, became filled up, and thus a well defined band was formed along the body whorL Genua 2.
Closely allied to the preceding. Order Nuclkobr anchiata or Heteropoda. Animals which possess a vertically, instead of, as in the snail, a laterally flattened foot, terminated by a fin-like tail, with which they propel themselves and swim near the surface of the sea. They are represented in Palaeozoic times by the following genera: Shell symmetrical; whorls few and keeled along the convex part of the shell.
Aperture generally expanded and deeply notched. Shell discoidal, grooved at the back, disc-shaped, left side flat, the dextral side, convex. Occurs chiefly at the base of the Lower Silurian. Shell symmetrical, thin, keeled, and curved in the shape of a horn. Shell thin, discoidal, unsymmetrical ; resembles that of Cyrtolitea, but the whorls are few and widely separated from each other.
This class is represented in the present day by two families whose habitat is far from land or oceanic. They propel themselves by two wing-shaped appendages, springing from the sides of the mouth, and possess a delicate glassy shell, resembling in form that of some Embryonic Cephalopods.
Their ancestors in Paleozoic times were of comparatively gigantic proportions, and were represented in the Silurian era by the three following genera. Shell bayonet-shaped or conical ; usually straight, but sometimes curved, thin, transversely striated or smooth, some- times with marginal ribs. Shell straight, tapering towards one end, and having a rhomboidal aperture at the other ; the sides composed of four plates united at their edges, and finely marked transversely with lines and dots. Conulariae of nearly a foot in length have been fotmd.
Genus 3 , — TentaetdiUs.
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This genus has been with con- siderable hesitation referred to the family of Pteropoda since it is doubtful whether its affinity is not rather with the Annelidea. Etheridge's opinion they should be removed to the group TubicoUe. The form of the shell is that of a straight conical tube, ornamented with a number of rings, the spaces between them often striated.
The size varies much, being sometimes less than two lines long, sometimes an inch or more. These are the most highly oiganised of the Mollusca. The body is symmetricaL The head is fiunished with eight, ten. The viscera, which are contained in a muscular sac, in some cases enclose a homy or calcareous bone, the pen of the Cuttle-fish , in others, are protected by an external shell, straight, or involute, which is divided into a succession of chambers by shelly septa ; a membranous tube called the Siphunde connects these chambers with each other and with the animal which occupies the last and largest, or body chamber.
The sheik of the Cephalopoda may be distinguished from those of the Gasteropoda by the presence of these chambers in combination with the stphuncle which the latter never possess.
The respiratory organs consist of two or four pairs of plume-like gills. No traces of the former are found in rocks earlier than the secondary. The Tetrabranchiata abotmded in the Palaeozoic and also in the Mesozoic epochs, but are represented from the Tertiary to the present time by but one genus only, that ot the Pearly Nautilus. The Dibranchiata propel themselves through the water by a jet which they have the power of emitting through the funnel, or they move along the bottom of the sea by means of their oial arms, which are furnished S2 with suckers.
With our scanty information about the internal structure of the Tetrabranchiata, it is not surprising that considerable diversity oi opinion exists among authors as to their classification. We shall in the following sketch adopt the arrangement of Mr. Blake, who has recently published an important monograph on this class.
The Tetrabranchiata are divided into two sub-orders: The former alone will be mentioned here since the latter did not make their appearance until after the close of the Carboniferous period. The NauliUAdea are divided into four groups. Curvature slight or none. Form conical and regular.
Siphuncle variable in position and structure. Aperture generally corresponds with the cross section, but is sometimes contracted. The surface of the shell is variously marked with strife, longitudinal and transverse ribs, and lamellse ; of which use is made in the determination of species. Siphuncle calcareous, central, cylindrical, and dilated between the chambers.
Differs from the former chiefly in the curvature of the shelL Whorls disjointed, the free end being elongated, septa simple or slightly waved, siphuncle dorsal. The main axis is straight The surface slightly marked by transverse sigmoidal striae. Siphuncle moniliform, generally central, or if sub- central, it approaches the convex side. Sq ta simple ; aperture contracted. Curvature well marked, septa simple, crossed by lines of growth ; aperture contracted in the middle, with larger openings at each end, the outer extremities lapping towards each other. The surface is generally ornamented by ribs undulating across the shell.
Body-chamber less in- flated than in Gomphoceras. Siphuncle generally internal or ventral, moniliform between the septa. The body chamber is inflated and gradually prolonged into a kind of neck.