416 MOLLUSCA. 



ever, are wanting, and the anterior muscular impression is not so 

 long(l). The genus 



Venus, Lin. 



Comprises many Testacea whose general character consists in the 

 teeth and plates of the hinge being approximated under the summit, 

 in a single group. They are usually more flattened and elongated, in 

 a direction parallel to the hinge, than the Cardia. The ribs, when 

 there are any, are almost always parallel to the edges, being directly 

 the reverse of their arrangement in the Cardia. 



The ligament frequently leaves an elliptical impression behind the 

 summits, which has received the appellation of vulva^ and before 

 these same summits there is almost always an oval impression term- 

 ed the anus or lunula{2). 



The animal is always furnished with two more or less protractile 

 tubes, sometimes united, and with a compressed foot, which enable 

 it to crawl. 



M. Lamarck appropriates the name of Venus to those which have 

 three small diverging teeth under the summit. This character is 

 particularly well marked in the oblong and slightly convex spe- 

 cies(3). 



Some of them the Astart^, Sowerb., or CRAssiNiE, Lam., have 

 only two diverging teeth on the hinge, and approach the Crassatellse 

 in their thickness and some other characters(4). 



Among the cordiform species, that is, those which are shorter 

 and have more convex nates, and with more closely approximated 

 teeth, we should remark those where the plates or transverse striae 

 terminate in crests(5) or tuberosities(6), and those that have longi- 

 tudinal ribs and crests elevated behind. 



(1) Ungulina transversa, Kam., Sowerb., Gen. of Shells, No. X. 



(2) These fantastic appellations of vulva and anus, have pi-obably caused the 

 extremity of the shell, which corresponds to the true anus of the animal, to be 

 styled the anterior, and that where the mouth is situated, the posterior. We 

 have restored to these extremities their true denominations. We must recollect 

 that thehgament is always on the posterior side of the summits. 



(3) Venus litterata, Chemn., VII, xh; V. rotunda, lb., xlii, 441; V. textilis, 

 lb., 442; V. decussata, xliii, 456, &c. 



(4) Venus scotica, Hans Lerin, VIII, tab. 2, f o\Crassina danmoniensis,ham.; 

 and among the fossil species, ^st. lucida, Sower., Min. Conch., II, pi. 137, f. 1; 

 Ast. Osmalii, Lajonkere, Soc. d'Hist. Nat. de Paris, I, tab. 6, f. 1. 



(5) Venus dysera, Chemn., VI, 27, 299iVen. plicata, Encyc pi. 275, 3, a, b, 

 Ven. crebisulica, lb., f. 4, 5, 6. 



(6) Venus puerpera, Encyc, 278; Fen. corbis, Lam., Encyc. pi. 276, f 4. 



