100 MOLLUSCA. 



their shell is of a very different form, being a triangle, of which the 

 obtuse angle is at the summit of the valves, and the base at their 

 edge, and of which the shortest side is that of the ligament, or the 

 posterior side, a rare circumstance in this degree, among bivalves. 

 They are generally small, and prettily striated from the summits to 

 the edges ; their animal PERONJEA, Poli, is furnished with long tubes 

 which are received into a sinus of the mantle. Some of them are 

 found on the coast of France*. The 



CYCLAS, Bmg. 



Separated from Venus by -Brugiere, like the Cardia and Donaces, 

 has two teeth in the middle of the hinge, and before and behind, two 

 salient, and sometimes crenulated plates ; but the shell, as in several 

 species of Venus, is more or less rounded, equilateral, and trans- 

 versely striated. The animal has moderate tubes. The external 

 tint is usually grey or greenish. The Cyclades inhabit fresh water. 



One species, the Tellina cornea, L.; Chemn., VI, xiii, 133, is 

 very common on the coast of France j\ M. Lamarck separates 

 the 



CTRKNA, Lam. 



Where the shell is thick, slightly triangular and oblique, covered 

 with an epidermis, and otherwise distinguished from the Cyclades by 

 having three cardinal teeth. The Cyrcnse also inhabit rivers, but 

 there are none in France J. 



CYPRINA, Lam. 



Also separated from the Cyclades by Lamarck ; the shell is thick, 

 oval, with recurved summits, and three stout teeth ; further back is 



* Donax rugosa, Cliemn., VI, xxv, 250 252 ; D. trunculns. Ib,, xxvi, 253, 

 254 ; D. striata, Knorr.. Delic., VI, xxviii, 8 ; D. denticulata, Chemu., I, c. 256, 

 257; D. faba, Ib., 266; D. spinosa, Ib., 258. Fossil species are numerous in 

 the environs of Paris. See Lamarck, Ann. du Mus., VIII, 139, and Deshayes, 

 Coq. foss. des Env. de Paris, I, pi. xvii, xviii. 



The Donax irrcgvlaris, from the Environs of Dax, described by M. Bastorat in 

 the Mm. de la Soc. d'Hist. Nat. de Paris, t. II, pi. iv, f. 19, A, B, is the type of a 

 new genus lately established Bullet, de la Soc. Lin. de Bourdeaux, II, by M. 

 Charles Desmoulins, under the name of GRATELUPIA. It is distinguished from the 

 Donaces by the presence of several dentiform lamellae which accompany the cardinal 

 teeth. 



Several species of Venus, and some Mactree, are mixed with these true Donaces by 

 Gmelin. 



f Add Tellina rivalis, Miill., Drap., X, 4, 5; Cyclas fontinalis, Drap., Ib., 

 8 12 ; Cycl. caliculata, Ib., 13, T4 ; Tellina lacustris, Gm., Chemn., XIII, 135 ; 

 Tell, amnica, Ib., 134; Tell, fluviatilis ; Tell, flutninalis, Chemn., VI, xxx, 

 320. 



I Tell, fluminea, Chemn., Ib., 322, 323; Venus coaxans, Id., xxxii, 336, or 

 Cyrena ceylanica, Lam., Encyc. Method., pen., pi. 302, f. 4 ; Venus borealis, Id., 

 VII, xxxix, 312, 314 ; Cyclas cardiniana, Bosc., Shells., Ill, xviii, 4. Fossil spe- 

 cies abound near Paris. See Deshayes, Coq. Foss., I, pi. 18, 1 J 



