38 THE NAUTILUS. 



would be an interesting task of Paleontology, to detect a fossil form, 

 or forms, from which the recent ones are derived. 



So far, it has not been possible to examine the soft parts and thus 

 complete our knowledge and description of the species ; but it is to 

 be expected that the necessary fresh, if possible living specimens will 

 be found, and I hereby w^ould invite the active collectors of the 

 north-western States to look specially for this Pupa, in order not 

 only to make a complete examination, but also to know more about 

 its geographical distribution, and possible variations. 



Description. 



Shell narrowly perforated, turrited-cylindrical, vitreous (or whit- 

 ish), very minutely striate, shining ; apex rather pointed ; whorls 5, 

 regularly increasing, well rounded, especially the upi)er ones, the last 

 somewhat narrowed and a little ascending towards the aperture, 

 compressed at the base but not carinated, at some distance from the 

 outer margin provided with an oblique, rather prominent, acute 

 crest corresponding in direction to the lines of growth, extending 

 from the base to the suture, formed by a Avhitish callosity ; behind the 

 crest the whorl is flattened, and corresponding to the lower palatal 

 lamella, impressed; aperture lateral, scarcely oblique, relatively 

 small, inverted subovate, w'ith a slight sinus at the upper part of 

 the outer wall, margins approximated ; peristome moderately re- 

 flected ; lamellje 6 ; one parietal, rather long, very high, in its 

 middle part curved outward, towards the aperture bifurcated, the 

 outer branch reaching the parietal wall ; one columellar, longitu- 

 dinal, rather high, its upper end turning in nearly a right angle 

 towards the aperture, but not reaching the margin ; basal exactly at 

 the base, short, high, dentiform ; 3 in the outer wall, viz. : the lower 

 palatal long ending in the callus, highest at about its middle ; the 

 upper short, rather high on the callous ; above the up})er one supra- 

 palatal, quite small, dentiform, nearer the margin. 



Length 1-7 mill., diam. O'S mill. (-068 x -032 inches). 



As already stated, our species ranges beside P. armifera and P. 

 contrada Say, standing nearer the latter. Yet it is diflerent from 

 this species by the shape of the aperture, the wanting callous* con- 

 necting the margins on the body whorl, by the longer crest behind 

 the aperture, which in contracta disappears in about the middle of 



* In many sptcimens of P. contracta so strongly developed, that the peri- 

 stome is rendered continuous. 



