76 HELIX. 



ed on the periphery. The axis is perforated, but generally closed in 

 the adult by the expansion of the columellar lip. The whorls num- 

 ber from 4 to 6, and are usually quite gradual in increase. The 

 aperture is usually wider than high ; peristome expanded, more or 

 less thickened, frequently bearing tubercular or lamellar teeth ; and 

 in Isomeria, Labyrinthus and some forms of Dentellaria, the parietal 

 wall also developes a tooth. 



I am altogether disposed to unite with this group the sections I 

 have separated under the name Thelidomus, viz. Thelidomus and 

 Parthena, with Polydontes, which is closely allied to the last-named 

 section. The essential identity of the two groups did not impress me 

 when preparing several months ago the part of the MANUAL, contain- 

 ing Thelidomus. The sections are numbered continuously from 

 Thelidomus, p. 56. 



With the addition of Oxychona, the group as here constituted is 

 synonymous with Fischer's subgenus Caracolus. 



The species of the various sections of Caracolus are distributed 

 throughout the West Indies and mainland of America from Brazil 

 and Peru to Central America. 



Synopsis of Sections. 

 Section III. POLYDONTES Montfort, 1810. 



Shell large, depressed, imperforate or narrowly umbilicate, solid, 

 heavy ; surface microscopically decussated ; whorls 4^-5, the last 

 slightly deflected anteriorly, carinated or rounded ; aperture oblique ; 

 peristome expanded, thickened, heavy, simple or with tubercular 

 obtuse teeth, columellar margin bearing an obtuse fold near its in- 

 sertion. Type, H. imperator Montf. 



Cuba. 



Section IV. DENTELLARIA Schumacher, 1817. 



Shell imperforate, solid, globose-depressed or conical-depressed, 

 often carinated, opaque, generally minutely granulated ; whorls 5 

 or less, slowly widening ; spire convex ; aperture transverse, wider 

 than high, oblique ; peristome more or less expanded, thickened ; 

 basal lip usually toothed. Type, H. nuxdenticulata Cheni. 



Lesser Antilles. 



Subsection GONOSTOMOPSIS Pilsbry, 1889. 



Shell narrowly umbilicated, rather thin, opaque, hirsute ; spire 

 depressed ; body-whorl rounded, depressed ; aperture as high as 



