DICERAS. 



Lam. 



TESTA inaequilateralis, inaequivalvis, umbone 

 alterius valvae affixa, dente magno, crasso, 

 concavo, subauriculari, in valva majore pro- 

 minente ; impressionibus 7nuscularihus in utraque 

 valva, duabus, lateralibus, distantibns : um- 

 bonibus magnis, divaricatis, spiraliter contor- 

 tis. 



We have already shewn that this Genus i:^ nearly related 

 to Chania, and we have advanced an opinion that it may 

 be regarded as forming a link connecting Isocardia with 

 Chama. Lamarck has associated it in the same family as 

 the last named Genus and observes that is differs so much 

 in its hinge and in its singular umbones that it appeared 

 to him to constitute a distinct Genus. We have never 

 seen the hinge, so that it is not possible for us to form our 

 judgment definitively; seeing, however, that the general 

 form of the shell, connected with the circumstance of its 

 being adhering by the point of the umbo of one valve, 

 renders it very peculiar we have thought it desirable 

 to give a representation of it. It appears to us probable 

 that it is only adherent, as Lamarck observes " in the 

 manner of the Gryphaeae,^' that is when in its young state, 

 for it is found to have been adherent by a small part of 

 the point of one of its umbones. Bruguiere did not think 

 it sufficiently different to separate it from the true Chamae. 



Shell inequilateral, inequivalve, one valve larger 

 than the other; attached by the point of the umbo of 



