TESTA aequivalvis, insequilatera, sub orbicularis 

 vel sub transversa; extus plus minusve radiatim 

 sulcata: margine crenulato. Denies in valva 

 altera duo, obliqui, alter elongatus, ci'assus; 

 alter subrectus, breviusculus : in altera dens 

 unicus, elongatus, crassus, obliquus. Impres- 

 siones museulares duse, subovales, laterales. 

 Impressio musculi adhaerentis pallii, Integra. 



Lamarck appears to us to have separated Venerieardia 

 from his Cardita without sufficient reason ; we have not 

 hesitated to unite them because we do not find any cha- 

 racter by which they can be distinguished. We wish, 

 however, to reserve our opinion upon such of his Carditae, 

 if indeed there be any such, as attach themselves by a 

 byssus in the same manner as the Mytili and the Arcce: 

 not that we have any further evidence of the existence 

 of such species than an observation of Lamarck, which 

 he only gives from hearsay, whereas he particularly 

 mentions in the generic character of his Cardita^ that it 

 is free. 



Shell equivalve, inequilateral, suborbicular, or some- 

 what transverse, with more or less strongly marked 

 grooves on the outside, passing from the umbo to the 

 upper margins ; which are crenulated within. Teeth in 

 one valve two, generally oblique, one of them elongated, 

 thick, mostly rather curved ; the other sometimes straight, 

 short, also thick; in the other valve one elongated, thick 

 and oblique tooth, and a deep elongated cavity for re- 

 ceiving the larger tooth of the other valve. There is 

 sometimes also another indistinct tooth in this valve. 

 Muscular impressions two, rather oval, lateral. Mus- 

 cular impression of the mantle entire. 



Very nearly related to Cypricardia of Lamarck, but 

 distinguished from that by the number of hinge teeth : 



