BOTHRIOPUPA. 227 



horizontally entering columellar lamella and subrnarginal 

 upper and lower palatal plica usually present, angular lamella 

 rarely developed. Type B. variolosa (GlcL). 



Distribution : tropical America. 



Illustrated on plates 28, 29. This small group of very rare 

 snails is probably to be regarded as a simplified derivative of 

 Gastrocopta in which the angular lamella has been reduced or 

 lost, and the lower palatal plica is nearly basal in position 

 and submarginal, not more deeply placed, as in Gastrocopta. 

 I am led to this view by the structure of B. geminidens, which 

 retains an angular lamella like Gastrocopta, while the rest of 

 the structure is that of Bothriopupa, and especially by B. 

 tenuidens, which sometimes has a well-developed though short 

 angular lamella, shown in pi. 29, figs. 12, 13. Moreover, the 

 species show several stages in the decadence of teeth, suggest- 

 ing that the ancestral form was a well-toothed Pupillid which 

 is evolving towards a Pupisoma-like form. 



The pitted or pock-marked surface of these species is highly 

 characteristic in the American series of Pupge, but it is 

 matched in the Nesopupa group, which in other respects does 

 not seem closely related to Bothriopupa. Most of the Bothrio- 

 pupte have reached about the same stage of tooth-reduction as 

 Gastrocopta quadridens; some have gone further. In teeth, 

 but not in sculpture, Bothriopupa resembles the East Indian 

 group Costigo. 



From the shape of the shell and its rarity in gatherings of 

 ground debris, I suspect that Bothriopupa will prove to live 

 on shrubs or on leaves, with the exception perhaps of B. gemi- 

 nidens. The single species which I have collected was found 

 dead on the ground. I would suggest beating foliage over an 

 inverted umbrella, or sweeping as for small insects, as pos- 

 sible methods of collecting. 



Probably these small snails will turn out to be widely and 

 generally spread in tropical America, when adequate atten- 

 tion is given to the minute shells, and their station is dis- 

 covered. 



This genus should have been inserted immediately after 

 Gastrocopta, but was omitted by oversight. 



