ACEPIIALA TESTACEA. 



O, J 



The Veni'sid.e (Venue, Linn.) — 

 Comprise many shells, whose common character is to have the teeth and lamina: of the hinge colli 

 under the heaks in a single group. They are in general flatter and more elongated in a direction 

 parallel with the hinge than the Cardia. Their rihs, when there are any, are almost always tran-\ 

 which is the contrary of the rule in the Cardia. The ligament often leaves, behind tin' beaks, an 

 elliptical impression, to which the term vulva has been applied; and in front of the beaks there is 

 almost always another oval impression that has heen called the anus.* The animal has always two tuhes, 

 capable of being more or less protruded beyond the shell, but they are sometimes united together 

 apparently in one; and it has also a compressed foot wherewith to crawl. 



M. de Lamarck restricts the name Vetnu to those which have three divergent teeth under the beaks. Thischa- 

 racter is peculiarly distinct in the species with an oblong, slightly convex shell. [These have been separated by 

 Sowerby to form bis genus PuBattra, to which he unites the Venerupit, Lam., believing that the latter do never 

 perforate rocks, but merely occupy the holes excavated by other animals.] Some (Attarle, Bow., or Crauitta, 

 Lain.) have only two diverging hinge teeth, and resemble the Crassatella in their thickness and some other 

 characters. Among the heart-shaped species it is important to notice those whose transverse ribs or stria' termi- 

 nate in crests or tuberosities on the posterior side ; and those which have longitudinal ribs and elevated crests. 

 I hey lead by degrees to the Cytherea, Lam., which has a fourth tooth upon the right valve, projecting under the 

 anus, and received in a corresponding fossa of the left valve. There are some species, as in Venus, of an elliptical 

 and elongated foi m, and others that are ventricose, among which is the famous species ( Venus Dionr, Linn.), that 

 originated the application of the name of the Goddess of Love to a shell, and remarkable for the long pointed 

 spines that guard its posterior end. There are species too of an orbicular form with slightly curved beaks, in 

 w Inch the impression of the retractor muscle of the tubes forms a large, almost rectilinear triangle. 



When the animals are better known, it is probable we may have to separate from Cytherea, — 1. The species of a 

 much compressed, lenticular shape, with beaks approximating to a point. There being no impression of the fold of 

 the cloak, we infer that the tubes are not extensile. 2. Thoseof a ventricose, orbicular form, which want the 

 impression just mentioned, but have a very long imprint of the anterior muscle, as in Lucina. 3. The thick species 

 with radiated ribs and without the impression of the cloak, which connect the Venusid.e with the Venericardia. 



There has been already ft pal ated from Venus the Capsa, Brug., which have on one side of the hinge tun teeth, 

 and on the other one only, but bifid ; the shell has no anus, is considerably convex, oblong, and the impression 

 left by the retraetor muscle of the foot is considerable ; anil the Petlicola, Lam., with two or thre» very distinct 

 teeth, one of them forked, on each side of the hinge. Their form is more or less cordate; but, as they live in 

 cavities of stone, [which they themselves perforate,] they become sometimes irregular. From the marks left on 

 the shell by the cloak, their tubes ought to be larger. 



The Vorkuta; Brug., similar in form to the triangular or heart-shaped Cytherex, have only a single strong tooth 

 in each valve, locking side by siile. The ligament is internal. The tubes ought to be short; and the valves are 

 rarely quite equal. The fossil species are much more numerous than those actually existing. Some live in the 

 interior of stones. [The 8phenia, Turton, separated from Corbula, and which has V. rostrata as its type, has not 

 been adopted by foreign Conchologists. Sowerby unites it to Mya.] 



The Mactraid.e (Mactra, Linn.) — 

 Are distinguished among the shells of this family because the ligament is internal, and is lodged on 

 both sides in a triangular fossa. They have all a compressed foot, fit to creep with. 



In Mactra, Lam., the ligament is attended in the left valve, on both sides, with a lateral tooth, winch locks 

 within two lamina? of the opposite valve. Close to the ligament there is on both valves a tooth which is folded 

 into the shape of the letter V, the point being nearest the ii m ho. The tulies are short and united. \\ e have some 



■pedes on our shores. f In the Lavignons [Listera, Turton] the lateral teeth are almost obliterated: nothing is 

 noticeable but a small tooth near the internal ligament, and we may remark also a small exterior ligament i the 



nor side of the shell is the shortest. The vah eg gape a little. The tuhes are separate and Verj long, as in 



'I ei: iua. one species {Mya kitpanica, Chemn.) is native, Living in the sand at the depth of several inches. 



THE FIFTH FAMILl OF Till', ACEPHALA TESTA! KA— 



Tin: Inc USA, — 

 II. is the cloak open at lie anterior end, or near the middle only, for the passage of the foot The 



opposite end is prolonged into a double tube, that can be pushed for beyond the shell. This is always 



• Thrie n.rm« are apt to mi > I end. anil are otherwi.e nbjecttonnbla. 



Thr .tioli-il ihoold ".it Ihr ligament ii alwnra ell I 



U> M ICtta, Ion imlilTi rrnllv <!. u 

 [\m> AmphMitmt 



'•e allitieil tO Mactra I bat tlirv 



o little hnown to aai i deSaltt plsct. [£rjrrfi 



>nuc well it . who hu characterised thrt • 



■ peele.. Tlic name anchor tin. nNn |riei n . k .,,...l deloltlon "I tmphi- 

 atom*, which i. aol m v.;,, ii. irith the Ltgmfat imi our limiti 



prevent ui ROtOf IMt'i ilrlr.il. C'li/e-i. ihnuld l.r 



near to Ani'iliiilcmft. It le reaaarka hie (Of the dlaelaatUrH] 



tinier ..I the tworelrea, oue baring a itrong lateral teeth on each • !"> 



■ 'I (he HfamtUt, mil lie "I Ltetal trrth. 



i dee are (bond In nod, in the Saaarei ol roclu, ami, ... lar aj >• 

 . Oirjr arc t r. j 



