118 [June, 



form a distinct group, holding an intermediate position between Clausilia and 

 Bulimus. 



Locality. Three miles below Fort Union. 



BULIMCS? VBRMICOLUS. 



Shell small, sinistral^ greatly elongated, cylindrical ; volutions about thirteen, 

 narrow, closely wound, increasing very gradually from the apex, somewhat con- 

 vex near the summit of the spirefbut flatteaed lower down; suture very faintly 

 impressed between the lower volutions, bat becoming more distinct above ; sur- 

 face marked with fine regular Hues of growth passing straight across the whorls 

 at right angles to the suture; aperture unknown. Length about -60 inch; 

 breadth -13 inch ; apical angle slightly convex, divergence 13. 



This is very near the last, and may be only a variety of the same. It differs, 

 however, in being more nearly cylindrical in form; the volutions are more nu- 

 merous, more closely wound, and do not increase so rapidly from the apes, 

 while the suture is less oblique, especially between the lower volutions. 



Locality and position. Same as last. 



Bulimus limneaformis. 



Shell narrow ovate, rather thick; spire conical, obtuse at the apex; volutions 

 Sve to five and a half, convex ; suture distinct ; surface marked with faint lines 

 of growth ; aperture ovate, angular above, rounded below; outer lip apparently 

 a little obtuse, or abruptly bevelled ; inner lip very thin on the body whorl above, 

 thicker and slightly reflexed below; columella regularly curved. Length -42 

 inch ; breadth -ZO inch; length of aperture -20 inch, breadth of do. -10 inch.; 

 apical angle corvex, divergence 38. 



From the same locality and position we have a single specimen agreeing in 

 ail respects with the above, excepting that the volutions are much flatter and 

 the suture less distinct. This may be another species, but without seeing more 

 specimens we are unable to satisfy ourselves it is not a variety of the same. 



Locality. Fort Clark. 



Bulimus Nebrascensis. 



Shell ovate ; spire rather short, conical, obtuse at the apex ; volutions fonr 

 and a half, convex ; suture distinctly impressed ; surface polished and marked 

 with nearly obsolete lines of growth ; outer lip apparently sharp ; inner lip very 

 thin above, thicker and slightly reflexed below ; aperture narrow ovate, acutelj' 

 angular above, somewhat narrowly rounded below. Length -27 inch ; breadth 

 -13 inch; length of aperture -15 inch, breadth of do. -07 inch; apical angle cob- 

 vex, divergence 47. 



It is possible this may be only a variety of the last, which it resembles in many 

 respects. It differs, however, in being a relatively thinner shell, has one whorJ 

 less, the spire is comparatively shorter, and the apical angle is considerably 

 greater. 



Locality and position. Same as last. 



Pupa helicoides. 



Shell very small, oval or ovate; spire moierately elevated, apparently obtuse 

 at the point ; volutions five, convex, increasing gradually from the apex ; surface 

 marked with strong lines of growth, which cross the whorls obliquely ; suture 

 distinctly impressed ; aperture very oblique, subcircular, rounded on the lower 

 and outer sides, nearly straight next the body whorl ; lip slightly reflexed ; um- 

 bilicus quite small. Length -12 inch ; breadth -08 inch ; length of aperture -05 

 inch, breadth of do. .04 inch. 



So far as we have been able to see from examining distorted specimens of 

 this species, it is without teeth. In this, as well as in many other respects, it 

 appears to have been very much like the recent /*. simplex (Gould,) but is about 



