104 



Mr. M. C. Marcli on the 



teeth of this suborder Bernard retains the name dysodont, 

 therefore it might he called the Dysodoiita. 



The second order Bernard called Heterodonta. Its two 

 main subdivisions he based on the fact that in one type 

 cardinal 1 is not differentiated from lamella 1, and therefore 



Fig. 8. 



Development oi Lucina neglecta. (After Bernard.) 



cardinal 2 is undivided. In the other type cardinal 1 is 

 present and cardinal 2 is divided. These two suborders 

 might perhaps be called Pliodonta and Oligodonta (figs. 8 

 &9)^ in reference to their diagnostic characters. The former 

 suborder is again divided into four classes : — 



1. Containing those forms which are typical of the sub- 



order (figs. 10& 11). 



2. Containing those forms in which CA 1 is either quite 



undeveloped or not strongly developed (fig. 12). 



3. Containing those forms in which the ligament is either 



entirely or nearly internal and where CA 1 is un- 

 developed (figs. 13 & 14). 



4. Containing Chaiiia and its allies (fig. 15). 



