U N I 



Species 310. (Mas. Sowerby.) 



Unio discus. Uh. testa oblongo-cimeatd, ponclerosd, con- 

 ceutrice rwjatd, nigra, intm purpurea, marg'me car- 

 diiiali crasso, detitibus posticis lam'math, anticis cras- 

 smdmis, laceraiis ; latere postico oblique angiilaio, gra- 

 datim angustato, margine dorsali decUvi, iermino 

 truncato, medio inflato ; latere aiitico bret'issimo, mar- 

 gine ventrali antice injlatu, postice ante angulim sub- 

 excavalo, umbonibus tumidis proitiineutibus. 



The disk Unio. Shell oblong-cuneate, ponderous, con- 

 ceuti-ically wrinkled, black, purple within, cardinal 

 margin thick, posterior teeth laminatetl, anterior 

 very thick, jagged ; posterior side obliquely angular, 

 gradually narrowed, dorsal margin sloped, the end 

 truncated, middle inflated ; anterior side very short, 

 ventral margin anteriorly iuHated, posteriorly in front 

 of the angle slightly excavated, umboes tumid, pro- 

 minent. 



Lea, Obs. on Unio, vol. ii. p. 74. pi. 18. p. 57. 



Hub. India. 



Species 311. (Mus. Taylor.) 



r.xio siNUATUS. Uii. tedct elongatd, reniformi, arcmtd, 

 rrannd, nigri'scenti, ad nmbones riifo-fuscatd, iiilus 

 alba, dentibufi crassis, laceratis ; latere postico arcua- 

 tiiii declivi, tumido, termino subrotundo, medio de- 

 presso, ad margiiiem wntralmn hiante profundi si- 

 niiato, unibonibus tumidis, prominentibus, lenuiter un- 

 dulatis, margine ventrali et termino rotundatis. 



The sinuated Unio. Shell elongated, reniform, arched, 

 thick, blackish, reddish-brown at the umboes, white 

 witliin, teeth thick, lacerated ; posterior side sloped 

 with a curve, tiuuid, subrotund at the end, middle 

 depressed, gaping, deeply sinuated at the ventral 

 margin, \nubocs tumid, prominent, finely undulated, 

 ventral margin ami end rouiidetl. 



Lamahck, Anim. sans vert., Unio, sp. I. 



[/nio Roissyi? et Unio elongatwi, Michaud. 

 Ilab. Rivers of Europe. 



It seems to me that this thick, arched shell diti'ers ma- 

 terially from the compressed and differently-formed Vain 

 iiiargaritiferus. The umboes are tumid and prominent, 

 and undulated, while in the British species they are ilat, 

 and scarcely produced beyond the dorsal outline. The an- 

 terior side rounded and full, instead of being narrowed and 

 compressed ; the sinus is deep, and the hiatus wide ; 

 while the posterior terminus is rounded instead of being 

 acuminated. 



Species 313. (]\Ius. Sowerby.) 



Unio ckassidens. Un. testa ovalo-subtrapezoided, jmu- 

 derosd, prope medium subtuberculatd, rugosd, nigres- 

 ceuti, intus albd, crassd, dentibus maguis, laceratis : 

 latere postico arcuatim biangulalo, inter angulos trun- 

 cato, margine dorsali declioi, ligameuto proiuineuti, 

 clongato, nmbonibus subtcrminalibus, autici declioi . 

 latere antico brevissimu, subrotundo. 



The tuick-toothed Unio. Shell ovate, tending to 

 trapezoidal, ponderous, slightly tuberculated towards 

 the middle, rugose, blackish, within white, thick, 

 teeth large, jagged ; posterior side with two arched 

 angles, truncated between the angles, dorsal margin 

 sloped, ligament prominent, elongated, umboes sub- 

 terminal, sloped in front ; anterior side very short , 

 rather round. 



Lamarck, Anim. sans vert,, Unio, no. 3. 



Ilab. Ohio River, Mississippi. 



This species varies in form, some specimens being more 



oval, with the umboes more sloped down towards the 



short anterior. 



Januarv, ISfiS. 



