scollops ; umbilicus moderately vVide, extending through t^ie truncate 

 apex. 



Mean divergence 75° ; length .55 inch ; greatest breadth .55 inch ; 

 least breadth .38 inch. 



The spiral lines, as usual in this group, do not appear on the first 

 whorl, but only on the last three. 



3. Cyclostoma aculeosum. Shell short, globose-conic ; dingy 

 white; with crowded transverse thin perpendicular lamella?, which are 

 decussated by numerous thin prominent spiral lines, with the points of 

 intersection produced into slender spines, especially in the angle of the 

 deep suture, the spiral lines appearing on the last three whorls ; spire 

 with very convex outlines ; apex truncate with the loss of two whorls, 

 three and one half whorls remaining, very convex ; last whorl a little 

 detached from the penult whorl near the aperture, but soldered to it by 

 the outer peritreme; aperture exactly circular; inner peritreme well 

 produced; outer peritreme well expanded, scolloped and striated as in 

 the preceding ; umbilicus moderately wide, extending through the 

 truncate apex. 



The spiral lamella of the operculum is extremely high and but 

 slightly reflected outwards. 



Mean divergence 77° ; length .56 inch ; greatest breadth .0 inch ; 

 least breadth .38 inch. 



4. Cyclostoma amabile. Shell globose-conic ; dingy or brownish 

 white, with the peritreme radiated w ith brown ; with very numerous 

 transverse thin perpendicular lamellse, which are decussated and acu- 

 leated by numerous spiral very delicate lines, which appear only on 

 the last three whorls ; spire with very convex outlines ; apex usually 

 truncate, with the loss of less than two whorls ; three and one half 

 whorls remaining, with a rather deep suture; last whorl not at all 

 detached from the penult whorl; aperture exactly circular; inner peri- 

 treme well produced ; outer peritreme greatly expanded, very deeply 

 striated with the lamellae of growth, which are pectinaied parallel to 

 the numerous scollops made by the ends of the spiral lines, perpendic- 

 ular and less developed against the penult whorl, sinuate and yet more 

 expanded above ; umbilicus exhibiting all the whorls and extending 

 through the truncate apex. 



The spiral lamella of the operculum is much less elevated than in 

 the preceding, and slopes outward much more. The sculpture of the 

 shell is finer, the umbilicus is narrower, and the peritreme is much 

 more expanded. 



Mean divergence 75' ; length .5 inch ; greatest breadth .55 inch ; 

 least breadth .35 inch. 



