UNIU.— Plate XXXV III. 



Troost's Unio. Shell shortly oval, thin, iuHated, white 

 within, olive without, anterior side rather short, nar- 

 row, round, middle very full, posterior side ratlier 

 broad, obtusely truncated, dorsal margin straight, 

 elevated at the back, ventral margin roinid, umboes 

 inflated, tuberculated. 



Lea, Trans. Amer. Phil. Soc. vol. v. t. 10. f. 30. 

 U. traialk, Conrad. 



ffai. North America. 



So light and thin as to resemble an Aiiodoii, but 

 although the hinge is very thin, it has lateral teeth. 



Species 311. (Mus. Cuming.) 



Unio Muulfeldianus. Uu. te.ild oUnuyd, subovali, 

 coiiipreud, ii/tus olid et pallide earned, extns fusco- 

 olivaced, nigra radiatd, coiicentrice sulcata, latere an- 

 tico brevi, rotunda, medio complanata, margine v/'i/trali 

 contracta, latere postico mhacuminata, area posterc- 

 dormli obliqud, compressd, aiigmtd. 



:Mu!ilfei,d's Unio. Shell oblong, rather oval, compressed, 

 white and pale flesh-coloured within, olive-brown 



without, rayed with black, concentrically grooved, 

 anterior side short, round, middle Hat, ventral mar- 

 gin contracted, posterior side subacuminated, postero- 

 dorsal area oblique, con)pressed, narrow. 



Lea. Trans. Amer. Phil. Soc. vol. vi. i'. 6. p. 41. 



Hah. Tennessee. 



Species 210. (Mus. Cuming.) 



LI NIC OBEsus. IJii. tedfi obloiigd, rhmiboided, mbcom- 

 pressa, teuui, intiin pallide ciipred, fxlns fiiaed, hexi- 

 gatd, latere aiUico brevi, aublniiicato, latere postico 

 oblongo, obscure biangidato, area pnstaiigulari hisid- 

 calo, murgbie terminali oblique sublruncato, margine 

 dorsalipaido elevalo,recliusr/ilo,wargine veiitrali recto. 



The obese Unio. Shell oblong, rhoinboidal, rather 

 compressed, thin, pale copper-coloured within, brown, 

 smooth without, anterior side short, subtnuicate, pos- 

 terior side oblong, obscurely biangulated, post-angular 

 area bisulcated, terminal margin obliquely subtrun- 

 cated, dorsal margin slightly elevated, rather straight, 

 ventral margin straight. 



Lea, Unio i. p. 106. pi. xiii. f. 2i). 



Hab. York River. 



