222 BULLiETEN 181, UlSIlTEiD STATEIS NlAmOiNlAiL MUSETJM 



Upper surface not malleated — Continued. 



Posterior angle of aperture auriculate — Continued. 

 Umbilicus not coarsely ribbed — Continued 

 Peristome notched — Continued 

 Notch of basal lip single. 



Height more than 30 mm bisinuatum 



Height less than 20 mm. 



Greater diameter more than 36 mm irregulare 



Greater diameter less than 30 mm pittieri 



Peristome not notched. 



Shell helicoid confusum 



Shell depressed-helicoid. 



Greater diameter more than 55 mm giganteum 



Greater diameter less than 50 mm. 



Greater diameter more than 42 mm. 



Umbilicus wide manabense 



Umbilicus not wide. 



Last whorl deflected fischeri 



Last whorl not deflected. 



Upper surface smoothish utriaense 



Upper surface rib-striate brujense 



Greater diameter less than 36 mm portobellense 



Posterior angle of aperture not auriculate. 

 Shell decidedly depressed. 



Base rather strongly axially ribbed. 



Aperture large fultoni 



Aperture small amazonense 



Base not strongly axially ribbed. 



Greater diameter more than 35 mm laxatvim 



Greater diameter less than 30 mm. 



Upper surface finely axially ribbed. 

 Axial ribs on periphery present. 



Suture narrowly channeled blanchetianum 



Suture not narrowly channeled peruense 



Axial ribs on periphery obsolete leai 



Upper surface obsoletely axially ribbed. 



Whorls downward sloping toward the su- 

 ture venezuelense 



Whorls not downward sloping toward the 



suture depressmn 



Shell not decidedly depressed. 

 Aperture large. 



Axial ribs of umbilical wall stronger than on upper 

 surface. 



Umbilicus narrow ecuadorense 



Umbilicus not narrow. 



Upper surface closely finely ribbed — subcingulatum 



Upper surface obsoletely finely ribbed quitense 



Axial ribs of umbilical wall not stronger than 

 those on upper surface. 

 Last whorl regularly finely ribbed. 



Shell pale olive colored olivaceuxa 



Shell brown castaneum. 



