126 THE NAUTILUS. 



Range: Indiana to Montana, south to New Mexico and Texas. 



Station : Same as humilis, curta, and the other small Lymnaeas. 



Remarks : This little species, the smallest of our American Lym- 

 naeas, is related to parva, appearing at first sight to be a small exam- 

 ple of that species. It differs from parva in its smaller size, rounder 

 and more turreted whorls, more slender outline, longer and narrower 

 aperture and smaller and less conspicuous umbilicus. The whorls 

 are inclined to be shouldered also, a feature not emphasized in parva. 

 There is some variation in the length of the spire, many specimens 

 having a rather long spire, while in others the spire is much 

 depressed, and the whorls are humped, this last being in slightly 

 abnormal forms. 



In THE NAUTILUS (xx, p. 52), this species was described as the 

 parva of Lea, but a careful study of Lea's types in the Smithsonian 

 Institution makes it evident that it is not that species, but a new one, 

 hitherto unnoticed. Young specimens of parva are similar to dalli, 

 but may be distinguished by the lesser number of whorls in shells of 

 the same size and in the different shape of the whorls. The two 

 small forms, parva and dalli, are related, but are easily separated 

 when attention is given to the details of form and size. 



This peculiar little species is named in honor of Dr. "William H. 

 Dall, Curator of the Division of Mollusks of the Smithsonian Insti- 

 tution. 



LYMN.EA LEAI n. sp. 



Shell large, ovate, thin ; color, yellowish-horn ; surface with fine 

 lines of growth crossed by equally fine spiral lines ; whorls 6, flatly 

 rounded, very rapidly increasing in diameter, the last whorl very 

 large ; spire short, broadly, ovately conical ; sutures well impressed ; 

 aperture elliptical or elongate-ovate, narrowed above, longer than the 

 spire ; outer lip thin, only slightly thickened by a longitudinal rib ; 

 inner lip thin, narrow, appressed to the umbilical region so as to 

 leave a well-marked chink ; callus on the parietal wall thin, wide, 

 well marked ; columella twisted, with a strongly developed ascend- 

 ing plait. 



Length 30, width 13.5, aperture length 18, width 8.5 mm. Type. 



Length 28, width 13.5, aperture length 17, width 8 mm. Type. 



Length 31, width 14.5, aperture length 18.5, width 9.5 mm. Type. 



Types: The Chicago Academy of Sciences; 1 specimen, cotypes, 

 collection W. A. Nason, 2 specimens. 



