10 



SYNOPSIS OF 





< 



< 



Eh 



PS 



Si 



in 

 Us 



W 

 C3 



1 . Subgenus Unio, 



Having a cardinal and lateral tooth. 



2. Subgenus Margaritana, 



Having one tooth (cardinal). 



3. Subgenus Dipsas, 



Having a linear tooth under the dor- 

 sal margin. 



Symphynote — Unio alatus,'' 



&c. 

 Non-Symphynote — U. picto- 



rum,'' &c. 



f Symphynote — Alas, compla- 

 nata,"" &c. 

 Non-Symphynote — Alas, un- 

 j^ dulata/ &c. 



Symphynote — Dipsas plica- 

 tus.'= 



ri. 





f Symphynote — Sym. magni- 

 Subgenus Anodonta, j fica/ &c. 



I Non-Symphynote — An. flu- 

 Having no teeth. ^ vlatills/ &C. 



Subgenus Iridina, f Non-Symphynote— I. exoti' 



I ca.*" 



Having a crenulate dorsal margin. [^ 



2. Subgenus Spatha, 



Having the dorsal margin non-cre- 

 nulate. 



Non-Symphynote — I. Niloti- 

 ca.' 



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. 



B Mytilus fluviatilis, Sol., Dill. &c. An. calaracta. Say. 



h Of Lamarck. 



* Of Sowerby, 



