VENUS. 



of the Genus as appear to be most natural. We shall 

 find that as in Cytherea the differences are principally 

 in the number and position of the teeth and in the siphonal 

 impression. The first and principal division of the Genus 

 consists of those species which are of a subovate form 

 and with the anterior side very much shorter than the 

 posterior; these are mostly longitudinally grooved or 

 lamellose on the outside, and they have three strong 

 diverging hinge teeth in each valve, the two anterior of 

 which are emarginate in one valve, and the two posterior 

 in the other valve ; in these the siphonal impression or 

 sinus in the muscular impression of the mantle is of mode- 

 rate size and rounded ; V, piierpera, V, reticulata, F, Corbis, 

 &c. belong to this division. 



The Venus flexuosa, V, Paphia, &c. are the typical 

 species of another division, whose form is somewhat 

 heart-shaped; they are generally rather acuminated 

 posteriorly and rounded anteriorly, and there is scarcely 

 any sinus discernible in the pallial impression; two large 

 and distinct diverging teeth in each valve, and one small 

 tooth which is anterior in the right and posterior in the 

 left valve. It is observable that Lamarck has placed one 

 of these (the V. flexuosa) among his Cythereai, and that 

 he has omitted the other ( F. Paphia ) altogether. 



A third division consists of such species as are nearly 

 of the same form as the last, but are covered externally 

 with thin distant lamellae; in these the sinus of the pallial 

 impression is very small, and acuminated anteriorly; there 

 are three cardinal teeth in each valve, of which the central 

 is large and thick, the others are small and thin, and the 

 anterior is a little curved ; the F. lamellosa and F. Thiara 

 are of this division. 



The fourth division contains Venus Marica and other 

 related species, which are rough and more or less cancel- 

 lated outside ; in one valve the middle and posterior teeth 

 are large, thick and emarginate, the anterior linear and 

 thin ; and in the left valve the anterior tooth is long, 

 thick and linear, the middle tooth is thick and emarginate, 

 and the posterior tooth small, linear, thin and scarcely 

 discernible, the pallial sinus is moderate in size and 

 rounded in front. 



