36 BULJMULUS-ANTILLEAN. 



that some species placed in Lissoacme may really belong to the re- 

 stricted subgenus Bulimulus. (Conf. Man. Couch. X, pp. 187-194). 

 The species of this subgenus are among the most difficult Buli- 

 muli to distinguish, being founded in most cases on slight and in- 

 conspicuous differences. It will readily be understood that too much 

 reliance should not be placed upon the "keys" I have attempted to 

 make. They merely offer suggestions. 



Antillean Species. 



With the exception of B. sepulcralis, which is most nearly allied 

 to Central American forms, the Antillean species form a moderately 

 homogenous group, having the apical sculpture more distinct than 

 in continental forms. 



a. Shell rather solid or thick. 



b. Often banded ; smoothish ; alt. 20-25 mill. exilis. 



bb. Opaque reddish brown or olivaceous, with puckered 



strise ; lip thickened within ; alt. 27-30 mill, nichollsi. 



bbb. Fossil; with low growth wrinkles, riisei. 



bbbb. Opaque whitish ; coarsely plicate, lehmanni. 



aa. Shell thin, more or less translucent, often with cuticular spirals. 



b. Aperture and diameter one-half the length of shell or 



more. 



c. Edge of lip very narrowly expanded ; whorls 

 about 5. 



d. Brown with light peripheral girdle ; per- 

 iphery subangular in front ; surface 

 with spiral cuticular line, semicinctus. 

 del. Brown with whitish dots, Iherminieri. 

 cc. Lip-edge not expanded. 



d. Alt. 14-15 mill. houelmontensis, 



dd. Alt. 20-21 mill. barbadensis. 



bb. Aperture less than half the alt. of shell. 



c. Peristome narrowly expanded ; whorls 7-8 ; no 

 spiral sculpture (?). limnoides, chrysalis, 



martinicensis. 

 cc. Peristome unexpanded, sharp. 



d. Aperture about i alt. ; alt. 19, diam. 7 



mill. mazei. 



dd. Aperture nearly J alt.; cuticular spirals 



present, fraterculus diaphanus. 



