convex, with a very deep suture ; last fourth part of the last whorl 

 diverging very abruptly and very far from the penult whorl; aperture 

 small, 'exactly circular ; inner peritreme moderately produced ; outer 

 peritreme enormously expanded, except on the inner side, convexly 

 reflected back of the plane of the aperture, smooth and shining, with 

 reddish brown rays; umbilicus narrow, but very plainly extending 

 through the truncate apex. 



Mean divergence about 35° ; length .56 inch ; greatest breadth .38 

 inch ; least breadth .27 inch. 



15. Cyclostoma Wilkinsonii. Shell small, subcylindrical ; whitish, 

 with a few small distant pale brown spots in a spiral series ; with not 

 very closely set sharp transverse raised lines; spire with slightly convex 

 outlines ; apex truncate with the loss of three whorls, of which the 

 second and tJdrd are seen in the young shell to be entirchj and widely 

 detached ; four whorls remaining, very convex, with a very deep suture; 

 last whorl widely detached from penult whorl near the aperture, 

 acutely angular above; aperture suborbicular, quite angular above; 

 inner peritreme moderately produced ; outer peritreme rather small, 

 concentrically striated, reflected a little back of the plane of the aper- 

 ture, above produced into an angle, with two or three small brown 

 spots ; umbilicus very small, but extending through and spreading 

 near the apex. 



Mean divergence about 17" ; length .35 inch; greatest breadth ,16 

 inch; least breadth .12 inch. 



16. CvcLosTOMA AVENA. Shell small, elongate ; whitish, more or 

 less tinged with brown, with numerous small distant brown dots in 

 spiral series on the lower whorls, on the upper whorls blueish gray ; 

 with closely set transverse moderately elevated lines, some of which, 

 in twos or rarely in threes, are more developed at the sutures into 

 small white crenulations ; spire with moderately convex outlines; apex 

 truncate with the loss of two or three whorls; about four and one-half 

 whorls remaining, very convex, with a deep suture ; last whorl much 

 detached from the penult whorl near the aperture ; aperture suborbicu- 

 lar, contracted a little on the left side ; inner peritreme a little pro- 

 duced ; outer peritreme rather small, much less extended on the left 

 than on the right side, not reflected quite back to the plane of the 

 aperture, produced above into a concave angle ; umbilicus very small. 



Mean divergence 23° ; length .32 inch ; greatest breadth .14 inch ; 

 least breadth .11 inch. 



17. Cyclostoma modestum. Shell small, elongate ; whitish ; with 

 thin raised lamina;, which are more distant on the upper whorls ; spire 

 with nioderalely convex outlines ; apex truncate with the lossof two or 



