GO 



LAND AND FRESII-WATER SHEW.S OF N. A. [PART II 



Kiininaea Vitrea, Haldeman. — Sliell ovate, extremely thin and 

 delicate ; surface smooth and polished ; lines of growth very fine ; aper- 

 ture ample: the labium presents a well marked fold, and is not 

 appressed anteriorly ; spire short. 



Ohio ? Missouri ? 



Foreign analogue, L. tenuis, Bronn. 



This species presents us with a shell which is probably thinner 

 in texture than that of any other we have. For the specimens 

 figured I am indebted to Mr. G. B. Emerson, President of the 

 Boston Society of Natural History. (Haldeman.) 



Limnsea vitrea, Haldeman, Mon. pt. 4, cover, p. 3 ; p. 47, pi. xiii, f. 14, 

 15 (1842).— DeKay, N. Y. Moll. 75 (1843). 



Fig. 93 is copied from Haldeman, whose description is given 

 above. 



Liininaea traskii, Tryon. — Shell elongated, the spire drawn out 

 and apex acute ; whirls six, convex, almost shouldered, sutures deeply 

 impressed ; aperture small, oval, labrum well rounded, labium 

 slightly rounded, not appressed below, not covering the umbili- 

 cus, which, though small, is very distinct. Color light horn or 

 cinereous. Length 16, diam. 8 ; of aperture, length 7, diam. 5 

 mill. 



Mountain Lake, California : Rev. J. Rowell. My cabinet, and 

 cabinet of Mr. Rowell. 



At first I was disposed to regard this shell as a variety of L. 



proxima. Lea, but a comparison with the type specimens of that 



species shows the following differences : the volutions are not so 



oblique, and are more rounded, the aperture is also more rounded, and 



the shell is umbilicated. Named in honor of Dr. J. B. Trask, one of the 



pioneers of Californian Conchology. {Tryon.) 



Limnxa traskii, Tkyon, Proc. Phila. A. N. S. 1863, 149, pi. i, f. 13. 



The above are copies of the original description and figure of 

 this species. 



Fig. 94. 



Fig. 95. 



L.imna?a pallida, Adams. — Shell moderately elongate, ovate- 

 fusiform, very pale horn color, semi-transparent, not very thin, 

 with fine, irregular striae of growth, without revolving stride ; 

 whirls about five and a half, moderately convex ; suture well 

 impressed ; spire four-ninths of the length of the shell, acutely 

 conic, its opposite sides containing an angle of about 450, Sub- 

 acute at tip ; body whirl not much enlarged, somewhat produced 

 below ; aperture five-ninths of the length of the shell, subovate- 

 acute above, angle of its plane with the axis of the shell about 

 IftOj of its length with the axis about 10^ ; labrum not thickened internally ; 



