THE CYCLOPHORID LAND MOLLUSKS OF AMEKODOA 187 



Genus APEROSTOMA Troschel 



1847. Aperostoma Teoschel, Zeitschr. Malak., vol. 4, p. 44. 



Aperostomine shells in which the heavy calcareous deposit of 

 adjacent turns of the operculum fuses. This deposit is a little higher 

 on the inner edge of the turns. 



Type : Aperostoma (Aperostoma) hlanchetianum (Moricand) . 



Distribution : Mexico to Brazil and the West Indies. 



KEY TO THE SUBGENERA OF MAINLAND APEROSTOMA 



Aperture with a notch at posterior angle Incidostoma 



Aperture without a notch at posterior angle. 



Sculpture engine-turned Austrocyclotus 



Sculpture not engine-turned. 



Sculpture anastomosing Neocyclotus 



Sculpture not anastomosing. 



Sculpture scalariform Cyclopomops 



Sculpture not scalariform. 



Periphery with color band Aperostoma 



Periphery without color band Cyclohidalgoa 



iNcmosTOMA, new subgenus 



Aperostomine shells of helicoid or depressed-helicoid shape. Spire 

 and base marked by slender, retractively curved axial riblets, which 

 are much stronger on the umbilical wall. The surface may or may 

 not be malleated. The posterior angle of the aperture in adult shells 

 is notched or even developed into a pseudosiphon. 



Type : Aperostoma {Incidostoma) malleatum^ new species. 



Distribution : Colombia, Ecuador, and Peru. 



KEY TO THE SPECIES OF THE SUBGENUS INCIDOSTOMA 



Greater diameter more than 45 mm. 

 Upper surface malleated. 



Malleations strong _ malleatum 



Malleations not strong pergrandis 



Upper surface not malleated. 



Diameter more than 53 mm kobelti 



Diameter less than 48 mm. 



Shell helicoid pichinchense 



Shell depressed-helicoid hedui 



Greater diameter less than 38 mm. 



Auricle very projecting incomptum 



Auricle not very projecting. 



Greater diameter more than 35 mm. 



Aperture very large pizarroi 



Aperture not very large. 



Suture deeply impressed nirafe 



Suture not deeply impressed hitomi 



Greater diameter less than 28 mm stirlingi 



