30 Unizrrsity of Michigan 



2. Group of Cyclostouia straminenm Reeve (1842). Shell 

 turbinate or depressed, usually unicolor; growth lines crossed 

 by oblique grooves and plicae, which break the sculpture into 

 rugae or granulations. Ecuador ( ?) ; Panama to Lesser An- 

 tilles. 



3. Group of Cyclostouia inca Orbigny (1835). Shell de- 

 pressed conoid, or with last whorl descending markedly (Cf. 

 Potcria confiisa) ; usually with darker, spiral bands; growth- 

 lines comparatively delicate and regular. Central America to 

 Brazil. 



4. Group of Cyclostouia incouiptiiui Sowerby (1849) from 

 Brazil. Shell similar to that of group 3. but with siphon-like 

 development of the upper edge of the peristome. Colombia to 

 Brazil. A', pcrgrandis Kobelt-Schwanheim (1912), from 

 "New Granada," is a larger shell than the typical species. 



In the localities studied, the forms of Poteria were found 

 to be remarkably limited in their distribution. In only one 

 place did two species occur together, and there the mixture 

 occurred only at the junction of two distinct habitats (H, I, 

 II, 42). In other localities, they showed a distinct tendency 

 to form small colonies. For instance, in all of the collections 

 made around Palma Sola, specimens of this genus were found 

 only in a single locality, and there appeared to be restricted to 

 an area about 20 meters across. The general appearance of 

 this area was the same as in many other portions of the sur- 

 rounding forest, which makes it especially difficult to account 

 for this peculiar localization. In all places, they were the 

 only snails that were common in the root humus ( H. I. II. c) ; 

 they seemed to favor especially the corners between the radiat- 

 ing roots and l)uttresses of the larger trees. 



