Chapter 30

[437]Histoire Naturelle des Crustacés Fossiles; par MM. Alex. Brongniart et Desmarest. 1 tom. 4to. Paris, 1822.

The fossil remains of Crustaceans consist of the calcareous covering or carapace, with the articulated extremities, and, rarely, the jaws and antennæ. For the most part, the specimens are mutilated, and present only portions of the carapace, abdominal segments, and detached claws; but in strata composed of very fine detritus, such as the cream-coloured limestones of Solenhofen and Pappenheim, examples often occur in the most beautiful state of preservation, appearing as if the animals had been carefully embalmed in a soft paste, that had quickly consolidated around them, and preserved them without mutilation or blemish. In some examples, even the colour of the original remains. The specimens found in hard limestones and coarse conglomerates are generally mutilated, and, as the under surface of the carapace, and the sternal plates to which the legs are attached, present more irregularity than the dorsal portion of the shell, they are firmly impacted in the stone, so as torender the development of some of the most important characters difficult, if not impossible. The antennæ and claws are often separated, or altogether wanting; the most common relics being the pincers and the carapace, or united cephalo-thoracic segments. The substance of the shell, which in the recent state consists of phosphate and carbonate of lime, with gelatine or cartilage, is commonly a friable carbonate of lime, tinged with oxide of iron. These remarks apply more particularly to the crabs, lobsters, shrimps, prawns, &c. Numerous species of the smaller crustaceans, as theCypris, and the extinct family ofTrilobites, occur in myriads, and, in some formations, are the principal constituent of deposits of great thickness and extent.

The remains of this class have been found throughout the vast series of the fossiliferous strata. Extinct forms appear in prodigious numbers in the most ancient formations, and are succeeded by genera which approach more nearly to the more highly organized crustaceans. The Crab and Lobster tribes are represented by certain species in the Lias, Oolite, and Chalk; while in many of the Tertiary strata the existing types prevail.

The London Clay, in the Isle of Sheppey, yields many beautiful examples of the higher order of crustaceans, as the Crab, Lobster, &c. In the Chalk these remains are more rare, but a few fine specimens have been obtained. On the Continent, certain localities are extremely rich in these remains. Upwards of sixty species were discovered by Count Münster in the Jura limestone, at Solenhofen; and the Muschelkalk of Germany has yielded several extinct genera. The beautiful state in which these fossils occur, is exemplified in the specimen from Solenhofen, figured in the frontispiece of this work;Pl. I. fig. 2.

Fossil Crabs.—Of thebrachyurous, or short-tailed, crustaceans, of which the common Crab is an example, and oftheAnomura(abnormal-tailed), there are remains of several genera in the Tertiary deposits. The Isle of Sheppey is the most productive locality in England. The carapaces of several kinds occur in the septaria and nodules of indurated clay; the chelate hand-claws (pincer-claws) are often found detached, and sometimes in connexion with the shield. The most numerous specimens are referable to two species. One of them (Cancer Leachii) is from two to three inches wide, and has a convex shell, the surface of which is covered by minute punctations, with three tubercles on each anterior lateral margin.[438]The carapace of the other species is more distinctly lobed, and studded with aculeated or spiny tubercles; it is namedC. tuberculatus.[439]

[438]Hist. Nat. Crust. Foss. pl. viii. figs. 5 and 6.[439]König, Icones Foss. Sect.fig.54. These two species are now referred to the genusZanthopsis.

[438]Hist. Nat. Crust. Foss. pl. viii. figs. 5 and 6.

[439]König, Icones Foss. Sect.fig.54. These two species are now referred to the genusZanthopsis.

A species of Crab, characterised by its relatively large claws, is common in the soft Tertiary limestone of Malta; and examples, in a fine state of preservation, are often seen in cabinets; seeWond.p. 251.

I am not aware that vestiges of more than one genus of brachyurous crustaceans have been observed in the British Secondary formations; namely, thePodopilumnus Fittoni(M‘Coy), from the Greensand of Lyme Regis: but several small species belonging to the anomurous group have been found in the Galt.

In theGaltat Ringmer, a village near Lewes, I discovered, many years since, four or five species of small crustaceans, which are figured and described,Foss. South D.pl. xxiv.; their natural relations were pointed out to me by the late eminent naturalist, Dr. Leach. Specimens of two of the species have since been collected at Folkstone, but as these are only the carapaces, no additional light has been thrown upon the structure of the originals.

The smallest species consists of the carapace or cephalo-thoracicsegments, united into a transversely obovate, obscurely trilobate shell, the surface of which is covered with minute irregular papillæ; with four tubercles on each lateral portion, and an irregularly tuberculated dorsal ridge (seeLign.168, fig. 1, 1a.); it probably belongs to the genusEtyus; and I have named itEtyus Martini, in honour of my friend,P. J. Martin, Esq., author of several excellent Memoirs on the Geology of Western Sussex.

Lign. 168. Fossil Crustaceans:nat.Galt.Near Lewes.]

[440]These two crustaceans are included in the fossil genusNotopocorystes, established by Professor M’Coy, 1849.

There are two species that appear to have some relations withCorystes, a genus which includes several recent crustaceans that inhabit our shores, and are characterised by theirelongated oval shell and four antennæ, the external pair being long, setaceous, and furnished with two rows of cilia. The tail is folded under the body when the animal is in repose. They have ten legs, the anterior pairchelate(with pincers), the others terminating in an acute elongated nail or claw. The fossils consist of the carapace, and one example possesses the inferior or thoracic plates and the remains of the bases of some of the legs (seeLign.168, fig. 3a).

Notopocorystes Stokesii.Lign. 168, fig. 2.—The carapace is relatively wider than in most species of this genus; is has a strong dorsal ridge of irregular oblong tubercles; the union of the cephalic and thoracic segments is marked by a transverse undulated groove; there are three or four tubercles on the surface of each lateral portion of the former, and one on each of the latter. The whole surface is finely granulated. The openings left by the attachment of the peduncles of the eye remain.

Notopocorystes Broderipii.Lign. 168, fig. 3.—This species, like the former, has a transverse undulated furrow, indicating the union of the cephalic with the thoracic segments; the dorsal ridge is smooth, and there are two tubercles on each lateral cephalic portion of the shield. The carapace is longitudinally ovate, much depressed, with three sharp points directed forwards on each margin of the anterior part: the whole surface is finely granulated. In the specimenfig.3athe sternal plates, with portions of the first joints of the claws, remain; one example (figuredGeol. S. E.p. 169) possessed six or seven arcuate abdominal segments, which were turned under the body.[441]

[441]I have described these small crustaceans somewhat minutely, and have given them specific names, in the hope of directing the attention of collectors to these highly interesting relics, and leading to the discovery of more illustrative examples. See Foss. South D. pp. 96, 97.

The carapace or shell of the other crustacean observed in the Sussex Galt (Notopocorystes Bechei) is of an orbicularinflated form (seeGeol. S. E.p. 169,fig.3), and ornamented with twelve or thirteen aculeated tubercles; its margin is dentated.

In the friable arenaceous limestone of the Cretaceous formation at St. Peter’s Mountain, near Maestricht, the cheliferous claws of a small kind of crustacean (Mesostylus Faujasii,Wond.p. 338), are frequently discovered (and occasionally in the Chalk of Kent and Sussex), but with no vestige of the carapace or shell. This curious fact is explained by the analogy existing between the fossil claws and those of thePagurus, or Hermit-crab, whose body is only covered by a delicate membrane, the claws alone having a calcareous covering; hence the latter might be preserved in a fossil state, while no traces of the soft parts remained. In the fossil, as in the recent claws, the right arm is the strongest. There is no doubt that the crustaceans to which the fossil claws belonged possessed the same modification of structure as the recent (anomurous) Hermit-crab, and must have sought shelter in the shells of the mollusks with which their durable remains are associated.

FOSSIL LOBSTERS.

Fossil Lobsters.—Themacrurous, or long-tailed, crustaceans, as theLobster, are distinguished from those of the former divisions by the prolonged abdomen (or tail, as it is commonly termed), which forms a powerful instrument of locomotion, and enables the animal to dart backwards through the water with great rapidity; and this is furnished with an appendage or tail, which none of the ambulatory crustaceans possess.

Of the fresh-water species, the Cray-fish (Astacus fluviatilis), and of the marine, the Lobster (Astacus marinus), are illustrative examples. The remains of three macrurous species occur in the London Clay of the Isle of Sheppey, associated with congenerous crustaceans; and the segments of the tails (post-abdomen) are often well preserved.

The Chalk contains a few species of theMacrura, which were first discovered in the quarries near Lewes, and are figured inFoss. South D.tab. xxx. xxxi.; they are among the most rare and delicate of the fossils of the Cretaceous strata. These remains consist of the carapace and claws, and rarely of the tail and antennæ, and are composed of a friable earthy crust, which, when first discovered, is of a dark chocolate colour, but quickly changes to a pale fawn, or reddish brown, by exposure to the air. In the specimens obtained by breaking the stone, the crustaceous covering remains attached by its rough external surface to one portion of chalk, and on the corresponding piece are sharp casts of the carapace and claws, having a glossy surface covered with minute papillæ formed by the bases of tubercles or spines. Four species have been observed.

Enoploclytia Leachii.Lign.169,figs.1, 2, 3.—This is a long delicate crustacean, having a pair of equal, slender, anterior chelate claws, the fingers of which are long, attenuated, and armed with a row of obtuse cylindrical spines. The surface of the hand-claws is muricated, or covered with short erect aculeated tubercles. The pincers in the specimen figuredLign.169,fig.3, are shorter than in most examples. The carapace is elongated and sub-cylindrical, with a dorsal ridge and two lateral furrows, indicating the normal division of the cephalic and thoracic segments of the shield; the antennæ are long, filiform, and setaceous (bristly), and are placed on squamous peduncles (seeLign.169,fig.2).

There appear to have been five legs on each side; the anterior or chelate pair are the most usual relics of this animal; of the other claws and the branchiæ, but obscure indications have been obtained. The abdominal segments are arcuate, and six or seven in number; their surface is granulated; the appendage, or tail, is foliaceous and marginate,with a few longitudinal ridges (seeLign.169,fig.1).[442]The claws of these crustaceans may be easily recognised by their general aspect, and the length and straightness of the fingers or pincers. In most examples traces remain of the tendinous expansion of the muscles of the moveable claw (seeLign.169,fig.3).

[442]See Foss. South D. p. 221,et seq.for further details.

Lign. 169. Fossil Crustaceans:nat.Chalk.Lewes.

[443]These fossil Lobsters are now to be referred to Prof. M’Coy’s genusEnoploclytia.

Enoploclytia Sussexiensis.Lign.169,fig.4.—The claws of this species are readily distinguished from the former by their broader and stronger proportions, and spinous character; the pincers are strong and tuberculated, and the moveable finger is more curved and shorter than its opponent. The entire crust of this lobster is muricated, or beset with spines and sharp tubercles.[444]

[444]Foss. South D. tab. xxx.fig.3. In the beautiful work of the late Mr. Dixon, on the Fossils of Sussex, there are figures of very fine specimens of these two species of Enoploclytia (plate xxxviii*.) with detailed descriptions by Prof. Bell (p. 344); but unfortunately, from inadvertence, no reference is made to my former drawings and descriptions of these fossil Lobsters of the Chalk, and new names are given by the Professor;E. Leachiiappearing as "Palæastacus macrodactylus," andE. Sussexiensisas "P. Dixoni." I need scarcely remind my readers that according to the established rules of Nomenclature theearlier specific namesmust be preserved; and that, Prof. M‘Coy having already indicated the distinction of these fossils from the recentAstacusby providing an appropriate generic appellation, these new names are altogether inadmissible.

Claws of otherAstacidæhave been found in the Chalk of Sussex and Kent; one species in particular is distinguished from those previously described by its short curved pincers, and granulated surface;[445]and remains of other species ofEnoploclytia, from near Cambridge and Maidstone, are described by Prof. M’Coy.

[445]This species may be namedAstacus cretosus, to indicate its geological habitat.

The "Lobster-clays" in the Lower Greensand, or Neocomian, beds at Atherfield afford numerous fine specimens of a small long-clawed crustacean, allied toAstacus; a fine specimen is figured in theGeology of the Isle of Wight, title-page vignette, and see page 232. One or more species, apparently distinct from those of Atherfield, have been discoveredby Mr. Beckles in beds of clay that appear to occupy the line of junction between the Wealden and Greensand, on the Sussex coast, between Pevensey and Bexhill.

Imperfect claws ofAstacidæhave also been found at other places in the Shanklin Sand; and I have collected from the Galt at Ringmer, the abdominal segments of a small species, resemblingMeyeria ornata,Lign.170.

Lign. 170. Fossil Crustacean.Speeton Clay.Yorkshire.Meyeria ornata:nat.(Phillips and M’Coy.)

The carapaces of two or three smallAstacidæ, sometimes with the abdominal segments attached, as in the beautiful fossil figured inLign.170, are found in the Speeton Clay, near Scarborough. In this example the post-abdomen and its appendages are entire, and traces remain of the antennæ and some of the feet. These specimens are commonly imbedded in masses of indurated clay, as the fern-leaves in the Carboniferous ironstone, and are discovered by splitting the nodules through their longest diameter. The carapace of another small species (Glyphea rostrata)[446]occurs in the Oolite of Scarborough. My friend, the Rev. J. B. Reade, has also discovered an example of this species in that rich repository of organic remains, the Kimmeridge Clay, at Hartwell, Bucks.

[446]This is theAstacus rostratusof Prof. Phillips’s Geol. York. vol. i. tab. 4,fig.20.

A remarkable macrurous crustacean (Eryon Cuvieri) is found in the Jurassic limestone of Solenhofen. Perfect specimens of this species are occasionally seen in collections; it is distinguished by its very large, flat, oval shell, with the front lateral margins strongly dentated, and by its short setaceous antennæ; the front claws are as long as the body, and armed with pincers; the post-abdomen consists of six segments, terminating in a caudal appendage or tail.

In the United States several fossil crustaceans have been noticed in the Cretaceous strata of New Jersey; some of which are said to be related toPagurus, and others toAstacus.

Fossil Prawns and Shrimps, of exquisite beauty, are found in the lithographic limestone of Pappenheim: a specimen from that locality (Palæmon spinipes) is figuredWond.p. 513: see also Frontispiece of this work.

A large crustacean of the Shrimp family has been discovered by the Earl of Enniskillen in the Lias of Lyme Regis.[447]Other specimens also of Macrura, more or less perfect, have been obtained from the same rich mine of organic remains: especially some in which thebranchiæ, or respiratory organs, remain; and a portion of the post-abdomen, or tail, of a Cray-fish, as large as the common species.

[447]This beautiful fossil is figured and described by Mr. Broderip, Geol. Trans, second series, vol. v. pl. xii. under the name ofColeia antiqua.

FOSSIL ISOPODOUS CRUSTACEANS.

Isopodous Crustaceans.Lign.171.—Isopoda(equal-feet) is the term applied to an order of crustaceans in which the body is composed of a distinct head, and seven rings, each having a pair of equal feet; the commonOniscus, or wood-louse, is a familiar example of a terrestrialIsopod. This order includes many genera and species, some of which nearlyapproach the extinct family of crustaceans (Trilobites) whose remains abound in the palæozoic strata; and the parasitical Isopod,Bopyrus, that infests the common Prawn, is closely related to certain genera of Trilobites, hereafter described.

Lign. 171.Archæoniscus Brodiei.Purbeck limestone.Vale of Wardour.(Drawn by S. P. Woodward, Esq.)Impressions of the upper and under surfaces.

One species of fossilIsopodhas been found in green fissile marl, at Montmartre; and another in fine-grained limestone, probably, from Pappenheim.[448]No fossil remains of this order had been noticed in the British strata, until the discovery of theArchæoniscusin the Purbeck strata by the Rev. P. B. Brodie. The quarry in which these relics were found is situated at Dallards, near the village of Dinton, about twelve miles west of Salisbury. They are principally distributed in a bed of light-brown and grey limestone, in the lower part of which are numerous fresh-water bivalves (cyclades), and a few small oysters. These Isopods often occur in clusters (seeLign.171); the lenses of the compound eyes are sometimes detectable in the limestone, and, rarely, attached to the head; traces of legs have been observed, but no antennæ. In the same stratum theelytron(sheath, or wing-case) of a coleopterous insect was discovered.Mr. Brodie has obtained specimens an inch and a half in length, and an inch broad. These fossils appear to have been deposited tranquilly at the bottom of the water which they inhabited, since they are usually found imbedded with their legs downwards, and generally well preserved.[449]

[448]Nat. Hist. Crust. Foss. p. 138.[449]See Brodie’s Fossil Insects, pp. 3 and 10.

[448]Nat. Hist. Crust. Foss. p. 138.

[449]See Brodie’s Fossil Insects, pp. 3 and 10.

TheArchæoniscialso occur in the Purbeck insectiferous limestone of Durlstone Bay, near Swanage, and have been discovered in strata of a similar character at the Ridgway railway-cutting between Dorchester and Weymouth, by the Rev. Osmond Fisher, of Dorchester.

Entomostraca.—The Crustaceans that we have above noticed belong to the Sub-classMalacostraca; and we have now to describe some fossil genera belonging to various divisions of the Entomostracous Crustaceans.

Lign. 172. Fossil. Limulus, in a Nodule of Ironstone:1/2nat.Carb.Coalbrook Dale.Fig.1.—Limulus Rotundatus, the imprint offig.3.2.—The nodule before it was broken.3.—Limulus Rotundatus, (the corresponding portion of the nodule,fig.1,) showing the entire form of the carapace.

FOSSIL LIMULUS.

TheLimulus(MolluccaorKing Crab) is a genus belonging to that Division of the Entomostraca termed Pœcilopoda and is abundant in the seas of India and America. Thecarapace is crustaceous and of a semilunar form, the head and thorax are blended together, and the superior abdominal shield, which is composed of confluent segments, appears like one piece, and has an indistinct trilobed character; the last segment is prolonged into a three-edged, sharp, styliform weapon. The Limulus has two reniform, compound eyes, composed of facets of a peculiar form. The gills are disposed on lamelliform processes. It is distinguished from all other crustaceans by the mastication of its food being performed by the first joint of the thoracic legs which surround the mouth, instead of by jaws.

Lign. 173. Limulus trilobitoides.Coal Measures.Coalbrook Dale.

Very fine examples of a fossil species of this remarkable genus are occasionally obtained from the lithographic stone of Solenhofen.[450]In England three small species have been discovered in nodules of ironstone and indurated clay, in the Carboniferous strata of Coalbrook Dale, by Mr. Prestwich.[451]In one example (L. Anthrax[452]) two of the legs are seen extending from under the body; in another species the sharp, pointed process of the tail is well developed (Buckl.p. 396, and tab. xlvi″.; see alsoLign.173). The specimen figuredLign.172is one of several examples which I obtained by breaking up nodules from that celebrated locality.Fig.2 represents the nodule unbroken, and without anyindication of its contents; by a well-directed blow it was separated into two equal portions,figs.1 and 3, in which the carapace of the crustacean, and its marginal appendages, are well displayed. The rounded form of the carapace, and the membrane which appears to connect the spines, separate this species from all others.

[450]Hist. Crust. Foss. pl. xi.fig.6.[451]See Mr. Prestwich’s Memoir on the Geology of Coalbrook Dale, Trans. Geol. Soc. second series, vol. v. part 3.[452]Trans. Geol. Soc. second series, vol. v. pl. xli. figs. 1-4.

[450]Hist. Crust. Foss. pl. xi.fig.6.

[451]See Mr. Prestwich’s Memoir on the Geology of Coalbrook Dale, Trans. Geol. Soc. second series, vol. v. part 3.

[452]Trans. Geol. Soc. second series, vol. v. pl. xli. figs. 1-4.

TheEurypterusand Pterygotus are palæozoic crustaceans, of large size. They are regarded by Prof. M‘Coy and Mr. Salter as belonging to the Pœcilopoda, and as differing from the Limulus chiefly in having the segments of the abdomen freely articulating with each other.[453]TheEurypteruswas first described by Mr. Dekay, in the United States, probably from the Carboniferous system. The head is round, the thoracic and cephalic portions of the carapace being blended together, and the abdominal region is formed of eleven segments, with a caudal appendage. It has two depressed, lunated eyes, remote from each other, and eight feet, the anterior pairs furnished withbranchiæ, and the hindmost pair relatively larger than in any other crustacean. Two American species are described; the one is five, and the other about four inches long.[454]In the Carboniferous strata at Burdie-house, near Edinburgh, and of Kirton, near Glasgow, a large species of this curious genius has been found by Dr. Hibbert and Dr. Scouler; the length of some specimens being estimated at from twelve to eighteen inches.[455]

[453]See Salter on Pterygotus, Quart. Journ. Geol. Soc. vol viii p. 387.[454]Dr. Harlan, in Trans. Geol. Soc. Pennsylvania, vol. i. p. 96.[455]See the elegant Memoir on the Fresh-water Limestone of Burdie-house, near Edinburgh, by Samuel Hibbert, M.D. F.E.S.E.

[453]See Salter on Pterygotus, Quart. Journ. Geol. Soc. vol viii p. 387.

[454]Dr. Harlan, in Trans. Geol. Soc. Pennsylvania, vol. i. p. 96.

[455]See the elegant Memoir on the Fresh-water Limestone of Burdie-house, near Edinburgh, by Samuel Hibbert, M.D. F.E.S.E.

Other species ofEurypterushave been noticed in the Upper Silurian rocks of Kendal, Westmoreland,[456]and of Kington, Radnorshire; and in the Devonian of Russia.

[456]Pal. Foss. Cambridge, Appendix.

Pterygotus.—In the Old Red sandstone of Forfarshire, and other parts of Scotland, the remains of this remarkable crustacean have been long known to the quarry-men by the name of "petrified Seraphims;" from an imaginary resemblance of the expanded post-abdomen to the usual representations of those ideal beings! This genus is characterised by the angular carapace, which forms a lozenge-shaped shield; and the appendage of the post-abdomen, which, instead of being divided into segments, as in most animals of this class, is a continuous flap. The eye-pits on the carapace are like those of Eurypterus, but are very large. The claws resemble those of the common lobster. The external crustaceous covering is ornamented with circular and elliptical markings, producing an imbricated or scaly appearance, the imprints of which gave rise to the enigmatical "Seraphims" of the Forfarshire sandstone. Some specimens indicate a total length of four feet![457]

[457]The Old Red Sandstone, or New Walks in an Old Field, by Hugh Miller, p. 147. There are specimens in the British Museum from the quarries of Carmylie.

Besides this Devonian species (P. anglicus), there is also a Silurian species (P. problematicus), from Herefordshire.[458]

[458]See Quart. Journ. Geol. Soc. vol. viii. p. 386.

Several fossil genera of the Entomostracous Crustaceans belong to thePhyllopoda(leaf-feet), which constitute a subdivision of theBranchiopoda(gill-feet). Of these perhaps the most remarkable is the Dithyrocaris, first discovered by Dr. Scouler in the Carboniferous shale near Paisley. This genus is allied to the recentApus, and, like it, has a broad, flat, thin carapace, easily divisible down the middle of the back, and a lengthened tail or post-abdomen, with a trifid termination. Six species have been found in the Carboniferous deposits of the British Isles.

Ceratiocaris and Hymenocaris, which are related to therecentNebalia, are also of the Phyllopod group, and maybe said to resemble a shrimp-like animal partly enclosed in a bivalve carapace, while its tail is exposed, and either protruded, or turned beneath the body. Of the first-mentioned genus there are three Upper Silurian species; and ofHymenocarisMr. Salter has described a single species (H. vermicanda) from the Lower Silurian (Cambrian) of North Wales.

TheLimnadiadæ,—another Phyllopodous family, of which the recentLimnadiais the type,—are well represented in the older rocks. These Crustaceans are also bivalved, but the body is wholly enclosed. They are of small size.Estheria, a genus closely related to Limnadia, occurs plentifully in the Wealden of Sussex and Germany, and in the Lias of Westbury. Mr. Bean also has noticed a species (E. concentrica) in the Oolite shell of Gristhorpe Bay; and theE. minuta[459]is characteristic of the Keuper division of the Trias in England and Europe.

[459]This was formerly described as aPosidonomya.

LeperditiaandBeyrichiaare other fossil genera belonging to theLimnadiadæ. These little crustaceans were gregarious in their habit, and, like Estheria, occur locally in great profusion. They are characteristic of the Silurian deposits; the former being an abundant Upper Silurian fossil in Europe and North America, and the latter,—a very minute form,—both in the Upper and Lower Silurian.

The next group of Entomostraca that we have to notice belongs to theLophyropoda(feet crested with bristles), namely, theOstracoda(shelled). The recent genera,Cypris,Cythere, andCypridina,[460]are types of the three families ofthis group, and are the existing representatives of numerous closely related forms that occur in a fossil state.

[460]The student should consult Dr. Baird’s elegant and elaborate work on the Natural History of the British Entomostraca (published by the Ray Society), for information on the characters and habits of these interesting little crustaceans and their numerous allies

Lign. 174. Fossil Cyprides.Wealden.Sussex and Isle of Wight.Fig.1.—Cypris Valdensis:magn.; showing the ventral aspect of the united valves.Cooksbridge.1a.—Side view of the same,magn.The three small figures are of thenat. size.2.—Cypris Fittoni,magn.Langton Green.3.—Cypris tuberculata,magn.Langton Green.3a.—View of the same, showing the lower edges of the valves united: the three small figures,nat.4.—Cypris granulosa,magn.; view showing the hinge-line.5.—A piece ofWeald Clay, with Cyprides and Shells;nat.

Cypris.Lign.174.—The animals of this genus belong to those Crustaceans in which the covering of the body is not divided into transverse segments, but consists of a large dorsal shield, having the form of a bivalve shell. They are often very minute, and numerous kinds swarm in our lakes and pools.The species of an allied genus, namedCythere, the shells of which cannot always with certainty be distinguished in a fossil state from those ofCypris, inhabit salt or brackish waters. As the livingCypridesare interesting objects for microscopic examination, they are commonly shown in the exhibitions of the hydro-oxygen microscope, and their appearance is therefore well known. Two recent species are figured inLy.p. 183. These animals have the body enclosed in a bivalve, horny case, the two pieces being united by a hinge-line. They have four feet, and two pairs of antennæ, with a pencil of cilia at the extremities; and one compound eye. They swim with rapidity, by means of their ciliated antennæ, and crawl about actively on the water-weeds and other subaqueous surfaces. Like the other crustaceans, they frequently moult or cast their cases, and the surface of the mud spread over the bottoms of still lakes is often covered with their exuviæ. The largest living Cypris (C. clavata) does not exceed one-eighth of an inch in length. The fossil cases or shells of Cyprides are found in considerable variety and in prodigious numbers in certain Tertiary and Secondary strata, which appear to have been deposited by fresh-water; as, for example, in the lacustrine marls of Auvergne (Ly.p. 183), and the fluviatile clays and limestones of the south-east of England. They have not been observed in any decidedly marine beds; but Mr. Lonsdale discovered in the Chalk, by means of the microscope, cases of crustaceans, that belong to the genusCythere(Ly.p. 26, figs. 21-24), the recent species of which inhabit the sea. One or more species of Cypris have been observed in the older British Tertiaries,—by Sir C. Lyell, in Hordwell Cliff (Geol. Trans.2d ser. vol. iii. p. 288), and by Mr. Prestwich at Hempstead Cliff (Brit. Assoc.1846); but in the Pleistocene deposits the Cypris and its congeners abound, and of these Mr. R. Jones has enumerated nine species (Annals Nat. Hist.2d ser. vol. iii.). In many districts on the Continent, theEocene marls and clays abound in these remains. Some of the fresh-water Tertiary strata of France contain myriads of a Cypris (namedC. faba, from its bean-like form) which was formerly supposed, but erroneously, to be identical with a species found in the Wealden. The laminated marls of Auvergne contain, between every layer, countless myriads of the shells of Cyprides, through a depth of several hundred feet; although each lamina of marl scarcely exceeds the thickness of paper. Near Clermont, the greencypridiferousmarls approach to within a few yards of the granite which forms the borders of that ancient basin (Ly.p. 184). In the eastern portion of the basaltic districts of India, Mr. Malcolmson has discovered two species of Cypris, associated with fresh-water univalves and bivalves.[461]In England the principal deposits of the Cyprides, are the clays and limestones of the Wealden and the Isle of Purbeck,[462]to the composition of which the relics of these minute beings have largely contributed. Entire layers of their cases are found in the laminated clays and marls on the southern shores of the Isle of Wight, at Atherfield and Sandown Bay, where some of the Wealden beds emerge from beneath the lower division of the Shanklin sand. Upon splitting the clay in the direction of the laminæ, the exposed surfaces are found to be covered with these minute bodies; as in the specimen,Lign.174, fig. 5.

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