606 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 54. 



In the flattening of the upper surface of the whorls the present 

 species suggests Pleurodonte {Gai^acollus) angistOTna Ferussac from 

 Haiti, but the under surface is entirely different, for in Pleurodonte 

 {Caracollus) angistoma there is no umbilical depression. The only 

 other form which approaches it in the flattening of the whorls is the 

 Haitian Pleurodonte {Caracollus) sarcocheila but even in that they 

 are not so flat as in the new form, nor does it have as strong an 

 umbilical depression as the present species; in that character this 

 approaches most nearly Pleurodonte {Caracollus) caracolla. 



It is quite possible that the present species is the fossil Pleurodonte 

 carocolla previously reported from St. Croix. The existence of a 

 member of the Caracollus section on this island argues strongly for 

 a former land connection from St. Croix to Porto Rico and the 

 island of Vieques, in both of which it is also represented, in spite 

 of the deep water existing at this present time between them and 

 St. Croix. Likewise, the presence of members of the group in Haiti 

 and Santo Domingo is equally strong evidence of former land con- 

 nection across the channel that now separates them. 



