BULIMULUS-BOSTRYX-LISSOACME. 155- 



The smooth apex is a perfectly constant and reliable diagnostic 

 feature ; but as few descriptions mention the minute sculpture of the 

 apex, it is impossible at present to classify with any degree of cer- 

 tainty, those forms not known to me by specimens. It will be 

 necessary to reexamine the types of a large number of species, in 

 order to discriminate between some forms of Sciitalus, Lissoacme f 

 Leptomerus and even Drymceus. Some thin species of Argentina and 

 Bolivia in particular are of doubtful position, and will remain so 

 until the characters of their apices are made known. 



The species are very numerous, and for the present may be thrown 

 into groups as follows : 



a. Adult shell strongly keeled ; surface malleated, 



Group of B. reentsi* 

 aa. Adult shell with rounded periphery. 



b. Outer lip expanded, Group of B. derelictus* 



bb. Outer lip not expanded. 



c. Surface wrinkled or striate, with no spiral lines, 



Group of B. hennahi* 

 cc. Surface wrinkled or striate, with spiral lines, 



Group of B. erythrostomus. 



ccc. Shell thin, unicolored or streaked, species of Argentina 

 and Bolivia, Group of B. apodemetes. 



Group of B. reentsi. 

 B. REENTSI Philippi. PI. 48, figs. 89, 90. 



Shell umbilicated, ovate-conic, keeled, solid and calcareous. Dull 

 white. Surface roughly sculptured with very irregular longitudinal 

 and short transverse wrinkles, having a crinkled or shrivelled 

 aspect. Spire conic ; apex mamillar, smooth and corneous, or some- 

 times eroded. Whorls 7, slightly convex, the last carinated at the 

 periphery, but slightly convex below, not excavated around the 

 rather narrow but deep and well-like umbilicus. 



Aperture less than half the length of shell, very oblique, subrbom- 

 boidal ; peristome white, sharp, the outer and basal lips expanded ; 

 columella straight, reflexed, the recurved margin wider above, partly 

 closing the umbilicus ; parietal wall calloused. Entire interior of 

 aperture deep purple and rose. 



Alt. 25, diam. 18 mill. 



Top of a lofty sand hill near Chala, Peru (Erneste Denicke). 



