118 



liEA S SYNOPSIS OF 







1. 



Subgenus Unio, 



Having a cardinal and lateral tooth 







2. 



Subgenus Margaritana, 



-51 



< 



o 

 < . 



H 

 C5 



3. 



Having one tooth (cardinal). 



Subgenus Dipsas, 



Having a linear tooth under the dor- 



52^ 



M 





sal margin. 













4. 



Subgenus Anodonta, 



<5 







Having no teeth. 





CO 



M 



cs 



1. 



Subgenus Iridina, 





5 



ij 



Q^ 





Having a crenulate dorsal margin. 







2. 



Subgenus Spatha, 









Having the dorsal margin non-cre- 



^ Sympbynote — Unio alatus," 

 I &c. 



1 Non-Symphjnote — U. picto- 

 [ rum," &c. 



I Symphynote — Alas, compla- 

 nata," &c. 

 Non-Symphynote — Alas, un- 

 [ dulata/ &c. 



Symphynote — Dipsas plica- 

 tus." 



I Symphynote — Sym. magni- 

 ! fica/ &c. 



1 Non-Symphynote — An. flu- 

 [ viatilis," &c. 



I Non-Symphynote — I. exoti- 

 j ca.'' 



Non-Symphynote — I. Niloti- 

 ca.* 



4 I 



nulate. 



After the divisions of Symphynote and Non-Symphynote shells, we 

 have what appears to me four very natural subdivisions, viz. 



a Of Say. 



•> Of Lamarck. 



•= Of Barnes. 



d Of Say. 



* Of Leach. Only two species yet known, this and S. discoidea, Lea. 



f Lea. 



6 3Tyfilus fluviatilis, Sol., Dill. &c. An. cataracta, Say, 



^ Of Lamarck. 



' Of Sowerby. 



