94 NILS HJ. ODHNEE, STUDIES ON RECENT CHAMIDAE. 



the hinge consists of 2 teeth in each valve; besides a posterior lateral there exists 

 an anterior one as well. On account of these facts I find it different from the 

 Chamidae, so that it cannot be included in this family nor be considered as a transi- 

 tional stage between these and the Carditidae. 



Among the recent Chamidae are to be reckoned only the genera included in 

 the conspectus given in the preceding chapter. 



Finally we may admit the possibility that both Veneridae and Cardiidae, 

 which, from an anatomical point of view, seem to have a common origin with 

 Chamidae, might have originated from forms closely related to the nepionic stages 

 prevailing in Chamidae, as the nepionic shell of a Pseudocliama reminds one of a 

 Venerupis and that of a Chama is like a Cardium. Both families appear at a relatively 

 late period, and their origin from Chamidae is admitted by paleontologists. No facts 

 on which an exact opinion on these questions can be based have hitherto been 

 presented, and both anatomical and ontogenetical investigations must be carried out 

 before we are able to judge with certainty about the mutual relations of Chamidae, 

 Cardiidae and Veneridae. 



Addenda. 



In a paper of 1917 entitled »Coquilles sénestres chez les lamellibranches» (Bull. 

 Mus. d'Hist. nat.) Lamy has given a close examination of the specimen of Tellina 

 plicata described as sinistral by Fischer 1880 (ef. above p. 7, note); the examination 

 makes it evident that no true inversion exists in this case, the hinge being entirely 

 normal. 



