460 Doll — Hinge of Pelecypods and its Develop m> nt. 



CLASS PELECYPODA. 

 Order Anomalodesmacea. 

 Suborders. 







Solenomyacea. 





Anatinacea. 

 My ace a. 



4. 



Ensiphonacea. 



5. 



Adesmacea. 



?y 









II. Order Prioi^odesmacea. 







Suborders. 



1. 



Nuculacea. 



5. Mytilacea. 



2. 



Arcacea. 



6. Pectinacea. 



3. 



Naiadacea. 



7. Anomiacea. 



4. 



Trigoniacea. 



S. Ostracea. 





III. " 



Order Teleodesmacea. 

 Suborders. 



1. 



Tellinacea. 



8. Leptonacea? 



2. 



Solenacea. 



9. Lucinacea. 



3. 



Mactracea. 



10. Isocardiacea? 



4. 



Carditacea. 



11. Veneracea. 



5. 



Cardiacea. 



* * 



6. 



Chamacea. 



? Rudista. 



7. 



Tridacnacea. 





Supplementary Note. — When I first began to consider the 

 relations of the teeth and other parts of the hinge, I naturally 

 remembered the brief abstract of the important paper on the 

 hinge of Bivalves by M. Neumayr which I had seen in the 

 Zoological Record for 1883. I intentionally deferred a careful 

 perusal of Neumayr's essay until I had entirely completed my 

 owd. Then a careful examination of his original afforded me 

 great pleasure. It showed that in the matter of the influence 

 of ribbing in promoting the nascence of teeth ; in the discrimi- 

 nation of lateral plications, arising' in connection with the fos- 

 sette of the cartilage, from the true cardinal teeth ; in the in- 

 fluence of the environment on the degeneration of hinge 

 characters : in the estimate of the characters of the primitive 

 bivalves ; and some minor points we had arrived independently 

 at the same conclusions and even illustrated them by identical 

 or nearly identical examples. This is certainly strong presump- 

 tive evidence of the correctness of those inferences. In the 

 points in which we differ, it seems to me that the differences 

 arise from the fact that Neumayr has approached the subject 

 more from the paleontological standpoint and has less consid- 



