II N I 



Spec-ies ii). Qhii. Ci.ini.iir.) 

 Unio HIPPOP^US. Uh. ksld ublouyu-uvuld, ijibboniusCKld, 

 iiiilice brevissimu, postici obtuse aiifjidatCi, ubnoleth 

 riule pUcatd ; castaneo-brunned. 

 The uokse-foot Unio. Shell oblong-ovate, rather gib- 

 l>ui.is, anteriorly very short, posteriorly obtusely an- 

 gled, obsoletely rudely plicated ; chestiiut-browu. 

 Lea, Trans. Amer. Phil. Soc, Second Series, vol. x. pi. 1. 



f. 1; Obs. vol. iv. p. 41. 

 Ilab. Lake Erie, North America. 



Of a peculiarly gibijose oblong-ovate lunu, largely ob- 

 liquely plaited, but the plaits are almost obsolete. 



Species 41. (Fig. a, b, JIu?. Cuming.) 

 Unio GIBBOSUS. Un. Usld nitbubloiiyo-urntu, jdiis lui/ius 

 caiwiformi, aiiiice breviuimd, po-^/ic- (Irrliri-aciniti- 

 imtd, vd comprfsse expansd, binidinliiit nidc Inbcrcn- 

 lald ; oUcactu-Inkd, viridi niiidi limari-radlatd. 

 The gibbous Unio. Shell somewhat oblong-ovate, more 

 or less wedge-shaped, anteriorly very short, poste- 

 riorly slopingly aeuuiiiialed, or conipressly expanded, 



biradiately rudely tubercled ; olive-yellow, neatly li- 



IUfinesuue, Mon. Coq. de la riv. Ohio, Ann. Gen. Sc. 

 Phys. Brux. 1820, vol. v. p. 387. 



Ilab. North America. 



The two forms of this species here tigured show how 

 materially the shell varies in its posterior growth. 



Species 42. (Mus. Cuming.) 



Unio perlensis. Un. testa suboblomjo-ovatd, crassd, 

 ffibbosissimd, postici arciiato-truncald, oblique pernm- 

 pliter plicatd, plicis versus iiiargiueM plus n/i/nis obso- 

 letis ; intense oUvaceo-uigrd. 



The solid Unio. Shell somewhat oblong-ovate, thick, 

 very gibbous, posteriorly arouately truncated, ob- 

 licpiely very largely plicated, plaits more or less ob- 

 .solete towards the margin ; dark olive-black. 



Conrad, Anthony, MS. in Mus. Cuming. 



Ihb. North America. 



Remarkable for its short, very gibbous jiruwth. 



August, 1864. 



