THE CYCIiOPHORID LAND M0LLUSK8 OF AMERICA 159 



cumingi, on the other hand, is marked on the entire upper surface 

 with equally strong spiral grooves which decrease in both directions 

 from the periphery, and form no cords on the umbilical wall. 



The shells described by Mousson were collected by Gustav Wallis 

 in northern South America. He collected in parts of Colombia, 

 Ecuador, and the Amazon region, according to Mousson's introductory 

 remarks. We have seen nothing like it. The spiral cords in the 

 umbilicus in a measure suggest Lagocyclus^ which has only a single 

 keel. 



Genus CALAPEROSTOMA Pilsbry 



1935. Calaperostoma Pilsbkt, Proc. Acad. Nat. Sci. Philadelphia, vol. 87, p. 4. 



Amphicyclotine shells of helicoid outline, spirally banded, having 

 spiral threads on spire and base, but not on the umbilical wall. 

 Operculum corneous, with the outer edge of the whorls upturned, 

 more or less regular, and marked by hairlike radial threads. 



G. hidalgoi (Crosse) has the radula formula 3:3:3:2, and the jaw 

 is without a median projection. 



Type: C diaper ostotna cumingi (Sowerby). 



Distribution: Panama to Peru. 



KEY TO THE SPECIES OF CALAPEROSTOMA ^ 



Spiral sculpture of last whorl strong. 



Posterior angle of aperture decidedly auriculate. 



Shell large, greater diameter 48 mm esmeraldense 



Shell smaller, greater diameter 32 mm rosenbergi 



Posterior angle of aperture not auricula ted. 

 Spiral keels evenly distributed on spire. 



Spiral keels on upper surface of last whorl 5 guayaquilense 



Spiral keels on upper surface of last whorl more 

 than 10. 



Shell very large, diameter more than 45 mm purum 



Shell smaller, diameter less than 35 mm. 

 Suture impressed. 



Greater diameter more than 25 mm. 



chanchapoyasense 



Greater diameter less than 20 mm bourcieri 



Suture not impressed pittieri 



Spiral keels not evenly distributed on spire. 



Greater diameter more than 35 mm nigrofasciatum 



Greater diameter less than 25 mm leai 



Spiral sculpture of last whorl not strong. 

 Umbilicus axially ribbed. 



Greater diameter more than 40 mm cousini 



Greater diameter less than 30 mm hidalgoi 



Umbilicus not axially ribbed cumingi 



1 0. ortignyi (Ancey) from Santa Cruz de la Sierra, Bolivia, is not included in this key 

 because of insufficient data. 



