102 CLASS I. TROPIOPODA. ORDER I. BIMUSCULOSA. 



altero subrecto, breviusculo ; in altera dente unico elongato, crasso, 

 obliquo. Impressio rauscularis pallii integra. Ligamentum ex- 

 ternum . 



The genus Cardita, as originally proposed by Bruguiere, included four 

 other well-known genera, instituted by Lamarck, Isocardia, Cypricardia, 

 Hiatella, and Venericardia. The first and second of these we readily 

 acknowledge ; the third, as we have already shown (vide p. 70), is but 

 the young of Saxicava rugosa ; and the fourth we re-unite to the Cardita?, 

 in accordance with the opinion of Sowerby and Deshayes. This last- 

 mentioned genus, Venericardia, was evidently selected by Lamarck, 

 because he considered its shell to be intermediate between that of the 

 Conchacea and the Cardiacea, and it was arranged by him in the first of 

 these families, under the impression that it partook more of the charac- 

 ters of that division. 



The shell of Cardita may be described as being equivalve, inequilate- 

 ral, suborbicular or transverse, with ribs or furrows diverging from the 

 umbones to the margin, leaving it crenulated. The hinge consists of 

 two oblique teeth in one valve, one of which is elongated and thick, the 

 other nearly straight and rather short ; in the other valve there is but 

 one thick oblique elongated tooth. The muscular impression of the 

 mantle is entire ; and the ligament is external. 



Examples. 

 PI. LXXIX. Fig. 1 and 2. 



Cardita calyculatus, Lamarck, Anim. sans vert., new edit., vol. vi. 



p. 431. Enc. Meth., pi. 233. f. 6. 

 Chama calyculata, Linnaeus. 

 Mytilicardia calyculata, De Blainville. (subgenus.) 



PL LXXIX. Fig. 3. 



Cardita sulcatus, Bruguiere, Enc. Meth. vers, vol. i. p. 405. La- 

 marck, Anim. sans vert., new edit., vol. vi. p. 426. 



