PUPA. 313 



other regions have been equally well explored. On 

 account of their minute size, they are not easily de- 

 tected ; but they have been found abundantly, in all 

 parts of the United States where they have been pro- 

 perly sought for. 



Rkmakks. This genus was first instituted by Drapar- 

 naud to include the minute species of Europe, of which 

 P. dolium is an exemplar. Previously, these shells had 

 been included in the genera Helix, Turbo, and Trochus, 

 from which they were very properly separated. Drapar- 

 naud intended it to include all the elongated, cylindrical 

 species, in which the whorls were very numerous, the 

 successive whorls differing but little from each other, and 

 the last one being but little larger, and often even 

 smaller, than the penultimate. The aperture in these 

 cases was also peculiar, being nearly circular, the lips 

 continuous, or nearly so, and the throat often armed 

 with denticles or folds. He, however, separated from 

 these, under the name Clausilia, those which he found to 

 possess a calcareous lid to the aperture, opening inwards 

 by a spring. Lamarck adopted these genera, but ex- 

 pressed his doubts as to the propriety of separating 

 ClausiUa from Pupa. Deshayes and others unite them 

 without hesitation ; but we still think that the shells 

 which possess the clausilium are entitled to rank as a 

 distinct genus, and that they have peculiarities, in other 

 respects, sufficiently marked to support this claim. 



We regard the genus as altogether an artificial one ; 

 VOL. II. 79 



