258 



disposfJ series of smooth oculiform tubercles; 

 braiictuai large, decomi)oaed into detached tilaracnts. 

 The loot sinail and dilated at its extremity ; mouth 

 rather laree, and oval, surrounded by projecting and 

 deeply-cut lips, and furnished on eacli side with a 

 p.^ir of triangular palps, tnmcated at their extremity. 

 The shell is f.ee, legular, and auiiculated ; umbones 

 contiguous; hinge toothless; the cardinal pit en- 

 tirely internal, and receiving the ligament. The 

 auricles or eailets of the shell are those projections 

 on each side of the umbo, extending some distance 

 downwards. . 



Mr. Garner, in his paper on the Ijimpllibrancliiata 

 ('Trans. Zoo). Soc.,' vol. ii.), considers the foot of 

 IVcten to be an organ for the prehension of food 

 collected by the vibratile currents near the mouth : 

 it has but one slender muscle. In one of the figures 

 accompanying his paper he delineates one of the 

 eye specks on the edge of the mantle, with its optic 

 nerve, magnilied. 



Speaking of the Laraellibranchiata generally, he 

 observes, that those species which, like the common 

 mussel, are exposed to the action of the sun and air 

 0:1 the bare rocks, have the valves tilting to each 

 other most exactly— preventing all evaporation ; but 

 when the valves are open at any part, the animal 

 either inhabits deep water, as many species of 

 Pecten. or has the power of burrowing in the mud 

 or sand when lell dry by the ebb of the tide. 



The scallops, as we have said, move rapidly back- 

 wards in an undating manner by flapping their 

 valves. Several species abound in our seas, and 

 some are considered as delicacies. The common 

 scallop, or St. .James's cockle (Pecten .Tacobieus), 

 when well treated by a good cook, is said to make a 

 rich and excellent dish. When so prepared, these 

 shell-fish are termed " Quins," in allusion to the 

 great tragedian and epicure, whose judgment in the 

 ilelicacies of the table was unquestioned. 



The shells of some species of Pecten are thick and 

 heavv, others again have the shell very light, and 

 some', as the Peeten vitreus (Gray), from the Arctic 

 Circle,* as transparent as glass. The determination 

 of the species, in many instances, is not easy. Some 

 are most beautifully coloured, but in others the tints 

 are sombre and unvariegated. 



2803. —The Common Scallop, or St. James's 

 Cockle 



{Pecten Jacobaeus). This shell, the well-known badge 

 of tlie pilgiimfrom the Holy Land, is common in 

 the seas of Europe and along our southern coasts. 

 Tne shell is unequivalve— the upper or left valve 

 being tlat, the under or right valve concave internally. 

 Each valve has from fourteen to sixteen angulated 

 rays; those of the lower valve are sulcated longitu- 

 dinally. It occure in a fossil state in tertiary de- 

 posits in Italy. 



2870. — ^The Flounder Scallop 

 (Pecten pleuronectes). This species is a native of 

 the Indian seas, and has its name from the circum- 

 stance of the upper valve being of a rich reddish- 

 brown, while the lower one is white — being thus bi- 

 coloured, like a flat-fish. The shell is subequivalve, 

 rather thin, smooth externally, somewhat convex on 

 both sides. 



2871.— The Gibbois Scallop 



(Perten giblwsus). The shell of this species is sub- 

 equivalve, ventricose, and red ; with from twenty to 

 twenty-two convex rays, somewhat rugose at their 

 sides and at the interstices. It is a native of the 

 Atlantic and American oceans. 



2872. — The Oebiculak Scallop 



(Pecten orbicularis). This species occurs only in a 

 fossil state, and is found in the chalk and other for- 

 mations in England and France. If is suboibicular, 

 with one valve smooth, the other marked with trans- 

 verse concentric striae. 



The fossil species of Pecten are veiy numerous, 

 as are those now existing. Of the latter, M. Dcs- 

 hayes enumerates thirteen as occurring also in a 

 fossil condition in tertiary strata. Fossil species are 

 found in the chalk, the oolite, and other ancient de- 

 posits. 



Closely allied to tlie genus Pecten is that termed 

 Hinnites. Though most naturalists assert that there 

 is no byssus in this genus by means of which the 

 animal moves itself to stones, Mr. Sowciby de- 

 cidedly asserts the existence of this natuial cable; 

 and though, from the singular manner in which the 

 shell becomes pressed to and takes the shape of the 

 substances to wliich it is pressed, its adhesion by 

 means of the valves is only apparent ; its real attach- 

 ment being by a byssus, and not by cement uniting 

 the shell to the rock. 



• An allipd tpeciM, Petflen vitrens of KiniJ'.not fJrty, was found 

 •verj where in the Strait of Maifellao, atUched to the fronds of Uie 

 Kiicoa gii^uti'Ui, and formed (rent put of tlic food of the Steamer- 

 Dttclt. 



MUSEUM OF ANIMATED NATURE. 



[Ghypii.ea. 



2873.— TnE Sisrocs Hissites j 



{Hinnites sinuosus). As an example of this genus 

 we give this species, the Pecten pusio of authors, 

 common in our British seas. The shell is ovate, 

 unequally sinuous, variegated with brownish orange 

 and white, and marked with numerous very narrow 

 reys like striw. ... 



A 8malk|umber only of living species belonging 

 to this gelw is known; and four or five fossil spe- 

 cies are found in some of the tertiary bed» of Franq^ 

 and Italy. 



Our next irpecimen belongs to the genus Lima. 

 In this genus the animal is oval, having the lobes of 

 the mantle separated nearly throughout their ex- 

 tent, larger than the valves of the shell, and turned 

 inwards ; this part of the border is wide, and fur- 

 nished throughout its extent with numerous tenta- 

 cular elongated and annulated cirrhi. Branchia; 

 rather large, equal, and separated (fcartees); foot 

 cylindrical, vermiform, rather club-shaped, and ter- 

 minating in a small sucker (ventouse), by means of 

 which the animal can fix itself to submarine bodies ; 

 no byssus; buccal aperture oval, furnished with 

 large' foliaceou^Bfcs, terminated on each side by 

 triangular and oBIiquely truncated labiij palps.— 

 (Deshayes.) Shell longitudinal, subequivalve, auii- 

 culated, rather gaping on one side of the valves; 

 umbones distant (ecartfes); their internal facets in- 

 cline inwards. Hinge toothless. Cardinal pit partly 

 external, receiving the ligament. 



In the .species of the genus Lima the foot has a 

 particular form. It is elongated, narrow, cylindrical, 

 and rather thickened at its free extremity, where it 

 terminates in a sort of sucker, which, according to 

 the observations of M. Quoy, serves to fix the aninia^ 

 upon solid bodies even of the most smooth surface. 

 The mouth is placed between two lips comparable 

 to those of Pinna : they are foliaceous, descend upon 

 the lateral parts of the body, and terminate on each 

 side in a pair of labial palps, which are truncated 

 and trianeular. The bianchise are rather large and 

 equal. The adductor muscle seems more extensible 

 than in the greater part of the mollusks of the same 

 class. When it is not contracted, the valves are 

 widely opened, and the animal has the power of im- 

 pressing on it frequent and sudden contractions, the 

 rapidity of which is facihtated by the extreme elas- 

 ticity of the ligament of the valves. By means of 

 these reiterated contractions the animal can flutter 

 in the water, to use the happy expression of M. 

 Quoy, and one must run after it to catch it among 

 the corals or in the shallows where it dwells. 

 Though the species are not numerous, the form is 

 widely spread, and is generally found in the seas of 

 warm and temperate climates. A few are natives of 

 the British seas. 



2874. — The Squamose Lima 

 (Lima squamosa). This species is a native of the 

 seas of America. The shell is oval and depressed ; 

 the hinge is oblique; the margin crenated: it ap- 

 pears as if clipped anteriorly. Colour white. The 

 ribsare squamous, rough, anti file-like. M. Deshayes 

 enumerates thirteen fossil species in tertiary beds. 

 One species is found in the inferior oolite. 



Another genus, belonging to the section em- 

 bracing the true Pectens, is that termed by Lamarck 

 Pedum. The mollusk of Pedum is thus charac- 

 terized by M. Deshayes :— Animal oval, oblong, 

 flattened, having the lobes of the mantle open 

 throughout their circumference, thickened on their 

 edges, and furnished on this part with many rows of 

 tentacular ciirlii, and, at regular distances, tubercles 

 with smooth surfaces. A pair of large branchiae 

 descending on each side to the edge of the lower 

 border of the mantle ; abdominal mass small, having 

 anteriorly and high up a small vcrniifoim foot, and 

 at its base a silky byssus of some size ; mouth oval, 

 having on each side a pair of labial liiangular palps. 

 (Deshayes.) 



With respect to the shell, Lamarck gives the fol- 

 lowing characters :— Shell incquivalve, subauricu- 

 late, lower valve gaping ; umbones unequal and 

 distant. Hinge toothless ; ligament partly external, 

 inserted in an elongated canalilbrm pit, which is 

 Allowed out in the internal wall of the umbones. 

 Lower valve notched near its posterior base. (Lam.) 



2875. — The Spondtloid Pedum 

 (Pedum spondyhtdcuvi). This is the only species, 

 we believe, at present known belonging to the 

 genus Pedum. It is described and figured by MM. 

 Quoy and Gaimard in the 'Zoology of the Voyage of 

 the Astrolabe.' It is a native of the Indian seas, the 

 coasts of the Isle of Fiance, and of the island of 

 Vanikoro, where the French nHturalists observed it 

 in great numbers, living partially encased in madre- 

 pores, such as Astraca;, &c. M. Quoy is of opinion 

 that the animal is capable of hollowing out excava- 

 tions in the blocks of madrepore, in which to take 

 up its residence ; and he found young and adult in- 

 dividuals tenanted holes proportionate to their re- 



spective sixes. M. Deshayes, indeed, seems to doubt 

 this burrowing power, antI suggests that the animal 

 having first attached itself to the coral, its shell 

 gradually becomes enveloped by the growth of the 

 coral. Granting, however, this to be the case, still 

 the young shell, which is enveloped, and inhabits a 

 cavity proportionate to its size, must have the means 

 of enlarging it according to its own increase ot 

 growth. The colour of the shell is whitish, tinged 

 with red ; the lower valve is the largest, with the 

 lateral edges turned up, and raised above those of 

 the superior valve ; the bys.sus pajises out through 

 tlK deep notch below the hinge of the lower shell. 



^Ve now come to the section of the Pectinic'a; 

 known as oysters, under which range several genera, 

 some of which, as Grypha'a, are found principally 

 in a fossil state, others, as Exogyra, only so. 



Between the genus Giypha-a and Ostrea there is 

 an insensible passage, so that in a large series of 

 species and varieties it would be impossible to draw 

 the line between the two genera. In both, the lower 

 valve is always the largest; in both, the hinge and 

 muscular impression are similar ; in both, the shells 

 during the period of youth are fixed tor a longer 

 or shorter period, becoming free as they advance 

 in age ; and even the involute curvature of the 

 umbo of Gryphapa, perhaps the strongest point 

 of distinction, is not constant in every species. 

 Hence M. Deshayes woidd abolish the genus alto- 

 gether, and with these views Mr. G. B. Sowerby coin- 

 cides. 



Provisionally retaining Gryphaea, we may observe, 

 that while the living species amount, we believe, 

 to only one (G. angulata), the fossil species are veiy 

 numerous, and are found in almost all strata down 

 to the lias inclusive. 



287(J. — The Iscvrved Gbiphjea 



(Gryphcca incurca). This fossil species is from the 

 lias. In his last edition of Lamarck, M. Deshayes 

 enumerates thirty-four fossils which Lamarck would 

 assign to this form. 



W hatever doubt there maybe about retaining the 

 genus Gryp'nsea, none exists with respect to the 

 untenahlenessof the genus Exogyra as distinct from 

 Ostrea. It possesses in fact no distinguishing charac- 

 ters at all ; although that eminent geologist Von 

 Buch regards it as clearly and decidedly separate. 

 The genus Exogyra was proposed by Say for such 

 species of Gryphaea as have the umbo taking a 

 lateral direction, instead of rising above the valves, 

 with a tendency to a dorsal angle, at least in some 

 species. The latter character therefore is by no 

 means constant; and with respect to the former, 

 many oysters exhibit the same tournure of the umbo, 

 though perhaps not carried out to the same extent. 



We have already stated that all the species attri- 

 buted to this genus are fossil. 



2877. — The Cosic.vl Exoqtba 

 (Exogyra conica). The example selected occurs in 

 the upper green-sand, gault, and lower green-sand. 



We now turn to the genus Ostrea, namely, that of 

 which the common oyster (ostrea edulis) is an ex- 

 ample. 



This genus is divided by many writers into two 

 groups: 1. True oystei-s, with simple or undulated, 

 but not plaited valves ; 2. True oystei-s, with the 

 borders of their valves distinctly plaited. 



To the first group belong the common oyster and 

 between thirty and forty living species, distributed 

 through various seas, principally in warm and 

 temperate latitudes ; no species appear to have 

 been discovered in the Polar Ocean. In the hotter 

 climates they abound, in sestuaries and along the 

 coast ; and are often found attached to rocks and 

 even to trees which border the water. In thisstrange 

 situation is taken the mangrove oyster of the West 

 Indies, so highly prized for its delicious flavour, and 

 in company with it a species of Pcrna, which is ac- 

 counted even still more excellent. An old traveller, 

 one William Davies, who quitted I'lngland on the 

 28th of January, 1597, is ridiculed by ah anonymous 

 writer in the ' New Monthly Magazine ' for 18C1), for 

 asserting that he had seen oysters and mussels grow- 

 ing upon trees, and eaten them ; as did also Obwer 

 Noore, a Dutchman (1GC5), in Guinea. The same 

 writer ridicules the idea of crabs feeding on the fruit 

 of trees ; yet oysters are found adhering to trees, and 

 there are tree-crabs (Birgus Latro) which feed on 

 the fiuit — consequently such ridicule proves only 

 that the writer's information in natural history was 

 very limited. 



2878.— The Cock's-Comb Ovstee 

 ( Ostrea Crista-Galli). This remarkable species is an 

 example of the second group, which contains more 

 than thirty recent species. It is a native of the Indian 

 seas. The shell varies in foun according to the shape 

 of the body to which it adheres, but is generally 

 somewliat rounded and very much plaited, the plaits 

 being longitudinal and angular. Exteraally the 

 colour is violet, purplish, or reddish white. 



