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Show 408 MOLLUSCA. CAsTALIA, Lam., Where the slightly codiform shell is striated in radii; the teeth and plates of the hinge are transversely sulcated, which gives them them some affinity with the Trigonire( 1 ). There are certain Marine Mollusca which have a similar animal, and about the same kind of hinge, that should be placed near the Unios; the summits of the shell, however, are more convex, and it is marked by projecting ribs extending from the summits to the edge. They form the CARD IT A, Brug.(2) Which are more or less oblong or codiform, the inferior margin, in sotne, gaping(3). CYPRICARDtA, Lam. Carditre, in which the tooth un.der the summit is divided into two or three. Their form is oblong, and their sides unequal( 4 ). M. de Blainville also separates the CoRALLlOPHAGA, Blainv., Where the shell is thin, and the lateral plate considerably effaced, which may cause their approximation to Venus. One of them is known which excavates coralline masses to form its habitation( 5). The VENERICARDIA, Lam. Only differ from the Carditre, in the circumstance that the pos· terior plate of. their hinge is shorter and more transverse, which caused their approximation to Venus; their form is almost round. (1) Castalia ambigua, Lam., Blainv., Malac., LXVII, 4. (2) Chama antiquata, Chemn., VI, xlvii,488-491;-Clt. trapezia;-Ch. semiur· biculata;-Ch. cordata, Id., 502, 503; and among the fossil species, one ofthe most singular, Cardita avicularia, Lam., Ann. du Mus., IX, pl.ix, f. 6, provided it should not be separated. (3) Chamacaliculata, Chemn., VII, i, 500, 501;-Cardita crassicosta, Brug., En· eye. pl. 234, f. 3. {4) Ohama oblonga, Gm., Chemn., VII, 1, 504, 505, or Cardita carinata, Encyc., pl. 234, f. 2, or Cypricarde de Guinee, Blainv ., Malac., LXV, his, f. 6. (5) Chama coralliophaga, Gm., Chemn., X, clxii, 1673, 1674, or Cardita dacty· Ius, Brug., Encyc., pl. 234, f. 5;-Coralliop'haga carditoi'des, lllainv., Malac., LXXVJ,3. ACEPHALA TESTACEA. 409 Judging from the impressions of its muscles on them, their animal must resemble that of the Carditre and U nios( 1 ). Both of them approach the Cardia in their general form and the direction of their ribs. I suspect that this is also the place for the CRASSATELLA, Lam.,-PAPHIA, Roiss., Which has sometimes been approximated to Mactra, and at others to Venus; the hinge has two slightly marked lateral teeth, and two very strong middle ones, behind which, extending to both sides, is a triangular cavity for an internal ligament. The valves become very thick by age, and the impression made by the margin of the mantle leads .to the belief that there are no protractile tu bes(2). FAMILY III. CHAMACEA. The mantle closed and perforated by three holes, through one of which passes the foot; the second furnishes an entrance and exit to the water requisite for respiration, and the third for the excretion of freces : these two latter are not prolonged into tubes as in the subsequent family. It only comprises the genus CHAMA, Lin., Where the hinge is very analogous to that of a Unio, that is to say, the left valve near the summit is provided with a tooth, and further back with a salient plate, which are received into corresponding fossre of the right valve. This genus has necessarily been divided into the TRIDACNA, Brug., The shell greatly elongated transversely, and equivalve; the su- (l) JTenus imbricata, Chemn., VJ, xxx, 314, 315, and the fossil species, Lam., Ann.du Mus., VII and IX, pl. xxxi and xxxii. (2) JTenus ponderosa, C:hemn., VII, lxix, A-D, or Cra8satella tumida, Lam., Ann. du Mus., VI, 408, 1; perhaps the Mact1·a cygnus, Chemn., VI, xxi, 207;Venuadivaricata, Chemn., VI, xxx, 3'17-319. This genus also comprises many fossil species, particularly abundant near Paris. See the work epf M. Desha yes. VoL. II.-3 B |