144 Contributions to Indian Malacology. [No. 2, 



No. 18. — Unio Theca., Bens. Kiver Cane near Banda, Bundelcund. 

 Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 186. 

 I have not seen this form. It belongs, according to Mr. Benson, 

 to the Corrianus type of Unio marginalis. 



No. 19. — Unio macilenttis, Bens. Choia Nuddy, near Bijnore, 

 Rohilcund. 



Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 187. 



A rather thin species resembling c&ruleus, but with stout hinge 

 teeth, resembling those of U. favidens. I am unacquainted with the 

 type, but a very similar form is common in the Damuda and its 

 tributaries in Bengal. 



No. 20. — Unio triembolus, Bens. B. Kamgunga, near Moradabad. 



Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 190. 



A thick shell with large hinge teeth. A massive species which 

 inhabits the Nerbudda, and the shells of which are found fossil 

 associated with the bones of extinct mammalia in the gravels of the 

 river valley, may be a variety of this species. I have never seen the 

 type. 



No. 21. — Unio plagiosoma, Bens. River Cane near Banda, Bundel- 

 cund. 



Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 191. 



No. 22. — Unio l^virostris, Bens. Near Chunar, in streams and 

 tanks. 



Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 191. 



No. 23. — Unio Pinax, Bens. Gungun stream, near Moradabad, 

 Bohilcund. 



Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 192. 



The three abovenamed species appear all to be allies of U. favidens. 

 They probably pass into each other. 



No. 24.— Unio Leioma, Bens. Deccan ? near Bombay. 

 Benson, Ann. and Mag. Nat. Hist. 1862, 3rd Ser. X. 192. 



The locality of this shell is uncertain. I have no species from 

 Western India which agrees with the description. 



