122 [June, 



distinct. By comparison, however, with authentic specimens of the latter in the 

 cabinet of Dr. Lea, at Philadelphia, we find his species is generally larger and 

 slightly more elongated than ours, and the body volution more rounded and 

 I'iss extended below. 



We name this species after Dr. Isaac Lea,, the well known conchologist, who 

 first made known one of its nearest living representatives. 



Locality. Fort Union. 



Paludina retosa. 



Shell obli([uely obovate ; spire depressed conical, obtuse at the apex ; volutions 

 fjur and a half to five, convex, last one large, obliquely depressed above, and 

 obscurely angular below ; suture well defined ; surface marked with distinct 

 oblique lines of growth, and faint traces of extremely fine revolving striae; 

 aperture (broad ovate?) obtusely angular above, rounded below; pillar lip 

 thin above, thicker and closely folded back upon the deeply arcuate columella 

 below. Length .84 inch ; breadth .64 inch ; apicial angle very convex, diver- 

 gence about 90. 



It is barely possible this may be one of the extreme varieties of the last ; it 

 differs however from any of the forms we have considered referable to that 

 species, in having a much less elevated and more obtuse spire. The lines of 

 growth also pass round the volutions much more obliquely, and the body volu- 

 tion is relatively larger. None of our specimens have the aperture entire. 



Locality. Three miles below Fort Union. 



Paludina Consadi. 



Shell elongate-trochiform, thick ; spire raher elevated, acute at the apex; 

 volu'ions apparently about six, flai, last one more or less angular below the 

 middle, and obliquely extended below ; surface marked with fine lines of growth, 

 crossed by delicate, nearly obsolete, revolving lines ; suture linear ; sperture sub- 

 circular, or broad ovate, obtusely angular above, (broadly rounded below?); 

 columella profoundly depressed in the umbilical region ; umbilicus none. Lergth 

 about 1 inch ; breadth -70 inch ; length of aperture -44 inch ; apical angle slight- 

 ly convex, divergence 54. 



In young specimens the angle on the lower part of the body whorl is quite dis- 

 tinct, and modifies the form of the aperture, but is more obscure in older shells. 

 Like P. Leui (of this paper), this species also has its near living representntives 

 amongst .Asiatic species, of which . Fra"cif>ci (Turbo Francisci of Wood,) is aa 

 example. We nume it in honor of Mr. T. A. Conrad, of Trenton New Jersey. 



Locality. Bad Lands of the Judith. 



Paludina peculiaris. 



Shell trochiform, rather thin, oblique ; spire conical, acute at apex; volutions 

 (five and a halt?) flattened convex, last one distinctly angular a little below the 

 middle ; surface marked with fine, rather indistinct lines of growth, crossed by 

 neaily obsolete, exceedingly fine revolving striae; suture moderatelj dtfined ; 

 aperture round ovate, or sub-quadrate. 



Our specimens of this species arc imperfect at both extremities ; some of them 

 have a breadth of 53 inch, and indicate a length of about -f inch The apical 

 angle of a specimen consisting of the lower two whorls is 47; but as it waa 

 probably greater near the apex, the mean may have been as great as 50. In 

 form and general appearance it is very much like the last, and may possibly 

 prove to be onl, a variety ot that species; it is, however, a thinner shell, and the 

 voluii'ms are more convex. 



Locality. Fort Claik. 



Paludina trochiformis. 



Shell trochiform, thin ; spire conical, pointed at the apex ; volutions five and a 

 half to i-ix, nearly flat, and ornamented by two slightly elevated revolving ririges; 

 last whorl strongly angular below the middle ; surface marked with ver\ fine lines 

 of growth, and exceedingly slender, raised, revolving lines ; suture linear, scarce- 



