54 CLASS I. TROPIOPODA. ORDER I. BIMUSCULOSA. 



CORBULA, Bruguiere. 



Testa insequivalvis, subglobosa, brevis, crassa, utroque latere clausa. 

 Dens cardinalis in utraque valva conicus, curvus, cochleariformis, 

 ascendens, cum foveola laterali adjecta, ligamento inserto. Im- 

 pressio muscularis pallii sinu parvo. 



To avoid unnecessary divisions, we have, in accordance with the opi- 

 nion of Deshayes, included the genera Corbula and Pandora in the 

 family of the Myaria. The distinction which Lamarck cites as peculiar 

 to his family of Corbulacea, which is made up of these two genera, is, 

 that their shells are inequivalve and irregular, characters which are com- 

 mon to many families of Bimuscular Tropiopoda. 



The shell of Corbula may be described as inequivalve, subglobose, 

 short, thick, and closed at the sides. In each valve, one of which is 

 often considerably larger than the other, is an elevated, conical, re- 

 curved, spoon-shaped tooth, with a deep pit on one side of it for the 

 insertion of the ligament. The muscular impression of the mantle ex- 

 hibits a small sinus. 



Examples. 



PI. XXXVI. Fig. 1. 



Corbula nucleus, Lamarck, Anim. sans vert., new edit., vol. v. p. 139. 



Enc. Me'th., pi. 230. f. 4. 

 Mya ineequivalvis, Montague. 



PI. XXXVI. Fig. 2 and 3. (fossil). 



Corbula Gallica, Lamarck, Anim. sans vert., new edit., vol. v. p. 140. 

 Enc. Meth., pi. 230. f. 5. 



