91 



intersections, into triangular points thickened at their bases : spire 

 short, with the outlines curvilinear: apex usually truncate, with 

 the loss of one and one half or two whorls : whorls remaining about 

 three and one-half, very convex, with a very deep suture ; last whorl 

 moderately detached from the penult whorl near the aperture: aper- 

 ture orbicular ; contracted slightly at the margin, which is neither 

 thickened nor expanded : umbilicus nearly half as wide as the last 

 whorl. Operculum with the upper edges of the whorls moderately ele- 

 vated into a spiral lamella, covered with irregular oblique lamellae, 

 extremely convex externally and concave internally : the diameter of 

 the operculum is .18 inch; the depth of the concavity from the inner 

 side is .07 inch ! 



Mean divergence about 85^ ; height .47 inch : greatest breadth .5 

 inch ; least breadth .385 inch. 



Ctclostoma NODDLostM. Shell elongate, ovate-conic : purple 

 at the apex and Iiehind the lip, with a few indistinct transverse spots 

 of purplish brown and an anterior spiral band of the same; with the 

 lip white : with very closely set strong transverse raised lines, which 

 are decussated by numerous spiral lines, with the intersections nodu- 

 lous : spire rather long, with the outlines scarcely curvilinear : apex 



truncate, with the loss of whorls : four whorls remaining, with a 



deep suture ; last whorl not detached from the penult whorl : aper- 

 ture ovate-orbicular: inner peritreme scarcely produced, but reflect- 

 ed: outer peritreme moderately expanded, well reflected, thick and 

 strong : umbilicus very narrow, but extending through the truncate 

 apex. 



Mean divergence about 35° ; height .53 inch ; greatest breadth 

 .34 inch ; least breadth .25 inch. 



Ctclostoia RETRORSUjr. Shell subovate : horn color, with 

 small irregular flames of brown, and a few small dots of the same, 

 which are inequidistant in spiral series : with numerous fine spiral 

 ridges, (of which one or two next the suture are larger), which are 

 decussated by numerous inequidistant moderately elevated lamellae, 

 •which are produced at the intersections into triangular points thicken- 

 ed at their bases : spire well lengthened, with the outlines quite cur- 

 vilinear : apex truncate, with the loss of whorls: remaining 



■whorls nearly four, very convex, with a deep suture ; last whorl not 

 separated from the penult whorl : aperture orbicular : inner peritreme 

 scarcely distinct from the outer, wdiich is thick and wide, finely radi- 

 ated with impressed lines, and reflected very far behind the plane of 



