FRESH WATER AM) LAND SHELLS. 261 



and slightly elevated; anterior cicatrices distinct; posterior cicatrices confluent; dorsal 

 cicatrices within the cavity of the beaks; cavity of the shell deep and rounded; cavity of 

 the beaks shallow and subjugular; nacre white and iridescent. 



Remarks. — A single adult specimen only has been received from Dr. Barratt, with two 

 quite young ones. The beaks of one of these arc sufficiently perfect to show that the 

 undulations extend some distance from the point, and that they are rather complex. The 

 young are rayed over the whole disk. The adult specimen has many dark-green ra\ s 

 over the posterior portion, but none on the anterior portion. This species is somewhat 

 like Unto cariosits, Say, but is more regularly elliptical and more transverse. The yen 

 specimens very much resemble the young of U. radiatus. 



Umo ineptus. PI. XV. Fig. 12. 



I \ta Isevi, eMpticd, mbcompressd ; valvulis tenuibus; natibus vlx prominentibus, ml in,ic<* undulalis; 

 epidermide valde tenebrosd, striata; dentibus cardinalibus parvis, compressis; lateralibus longis, subrect 

 cardincdibus separalis; margaritd cxruled. 



Shell smooth, elliptical, somewhat compressed; valves thin; beaks scarcely prominent, undulated at the bea 

 epidermis very dark and striated; cardinal teeth small, compressed; lateral teeth long, nearly straight and - 

 rated from the cardinal tooth; nacre bluish. 



I lab. Abbeville District, S. C. J. P. Barratt, M. D. 

 My cabinet. 

 Diam. .4, Length .7, Breadth 1.3 inches. 



Shell smooth, elliptical, somewhat compressed, rounded before and subangular behind; 

 substance of the shell thin; beaks small, scarcely prominent; undulated rather coarsely at 

 the tip; ligament short and thin; epidermis much striated, very dark-brown, nearly black; 

 umbonial slope rounded; marks of growth indistinct; cardinal teeth small, compressed, 

 crenulate, double in the left and single in the right valve; lateral teelh long, nearly straight, 

 thickened at the posterior end; anterior cicatrices distinct; posterior cicatrices continent ; 

 dorsal cicatrices placed nearly in the centre of the cavity of the beaks; cavity of the shell 

 \> ry shallow; cavity of the beaks very shallow and angular; nacre bluish. 



Remarks. — A Bingle specimen only of this species is before me, and may not be adult. 

 It is quite small, and somewhat like I . fabalis, (Nobis,) of our western rivers, but is still 

 more closely allied, in general form and colour, to U.faba, D'Orb. It. differs from the 

 former in being a thin shell, and having a more elevated posterior slope, and from the 

 latter in having the sides more compressed, and in the beaks having irregular undulations, 

 v\hile the /aba bas the radiated folds so peculiar to most of the South American species. 

 The specimen of ineptus bef>»re mc has two obscure rays on the posterior slope, none being 

 apparent over the disk. More perfect specimens may present rays 



IMo mnasoB. PI. XV. Fig. 13. 



I Uni, eUiptted, tubinflalA } oalvuli ibprominentibus ; epidermide leneb 



dentibus cardinalibus nibparvit ereclisqut .- lateralibus longit lubreetitqut ; m ''"' (/ iridescente. 



VOL. X. 50 



