154 Descriptions of Neiv Species and Varieties of Shells, 



soldered to it by the outer peritreme : aperture circular ; inner 

 peritreme moderately produced ; outer peritreme much ex- 

 panded, and reflected very convexly back of the plane of the 

 aperture ; imbricate, slightly and finely scolloped : umbilicus 

 not very wide, extending through the truncate apex. 



Mean divergence about 75° ; length .54 inch ; greatest 

 breadth .53 inch ; least breadth .38 inch. 



Operculum very convex, very closely striated obliquely, 

 with the spiral lamella moderately raised. 



This shell closely resembles C. spinulosum, except in the 

 outer peritreme and in the operculum, Avhich widely distin- 

 guish it from the allied species. The operculum, however, 

 somewhat resembles that of C. anomalum, and the lip is like 

 that of C. retrorsum. 



The species is named in honor of Professor A. H. Mousson 

 of Zurich, Switzerland. 



Cyclostoma amandiim (p. 3 of C. C.) is probably identical 

 with C. scabriculum, Sowb. 



Cyclostoma virg-ineum (p. 90, C. C.) is identical with C. 

 pi sum (p. 9.) 



Cyclostoma concentricum (p. 4, C. C.) is not sufficiently 

 distinct from C. variabile (p. 3, C. C.) to take a higher rank 

 than that of a variety. 



Cyclostoma mutatum. This name is here proposed for C. 

 articulatum Sowb., inasmuch as G-ray in Griffith's Cuvier 

 (1836) had already applied the latter title to a species after- 

 wards known as C. filoswn Sowb. Sowerby's C. articulatum 

 was not established until 1843, and must therefore be dropped. 



Cyclostoma Campbellii. Shell elongate conic : color ? 

 with numerous transverse moderately elevated lamellae : apex 

 acute : spire not truncated, with the outlines but little convex : 

 whorls six and one-half, quite convex, with a rather deep su- 

 ture ; last whorl at the end much detached from the penult 

 whorl, and angular above : aperture nearly circular, with the 



