

MANUAL OF CONCHOLOGY. 



FAMILY HELICID^E, Vol. III. 



Genus HELIX, Linn. 



Group XL HEMITROCHUS Swainson, 1840. 



The subgenera or sections which I have assembled under the 

 above name, form a perfectly natural group, allied as well by the 

 characters of the soft parts (as far as these are known) as by the 

 shells. The group includes some of the most brilliantly painted of 

 all Helices. Unlike shells of the groups Pentatcenia and Arionta 

 the decoration of these forms follows no rule as to the number and 

 disposition of bands. The surface is smooth or simply obliquely 

 striate, never granulated ; the lip is simple, acute, or expanded 

 and thickened ; the aperture is not obstructed by teeth except in 

 some species of Plagioptycha. All of the species are confined to the 

 West Indian islands from Hayti and Jamaica northward, including 

 the Bahamas. H. varians Mke. is the only species found upon the 

 mainland of America; and its range does not extend further north 

 than the southern extremity of Florida. 



This Group is composed of part of the elements included by 

 Fischer in each of his subgenera Helicogena and Polymita. (Man- 

 uel de Conch., p. 471). 



Synopsis of Sections. 



Section I. CYSTICOPSIS Morch. 



Shell imperforate or narrowly perforate, globose or globose-de 

 pressed, generally thin ; last whorl not descending at the aperture ; 

 peristome acute ; not expanded or thickened within ; columellar 

 margin arcuate, not flattened, somewhat expanded above. Type, H. 

 cubensis Pfr, 



Cuba, Hayti, Jamaica. 

 (5) 



