General Claasification of the Pelecypoda. 



97 



taxodont form. Dall noticed the same origin for the 

 Anisoinyariaa teeth ; but he read it as excluding them 

 from any connection with the Taxodonta, whose teeth he 



Young stages oi Area. (After Bernard.) 

 C = band of crenulations; Li = primary ligamental pit; L — liganieqt. 



Avmila microptera (after Bernard^, showing tlie dysodont teeth, which 

 anteriorly show a tendency to produce cardinals, 



conceived as arising perpendicular to the hinge-line, Con« 

 firming the fact that the dysodont stage precedes the taxas 

 dont, Bernard cites the case of the development of those youug 

 Ann, ct- Mag, X Hist. Ser. 8. Vol, x. 7 



