THE CYOLOPHORID LAND M0LLUSK9 OF AMERICA 259 



retractively curved feeble riblets, which are rather irregular in 

 strength and spacing, and which become weaker on the last turn 

 and obsolete on the last portion thereof. Suture well impressed. 

 Periphery weakly angulated. Base narrowly umbilicated, inflated, 

 strongly rounded, and marked by the continuation of the feeble axial 

 sculpture, which, however, develops into stronger and broader riblets 

 on the umbilical wall. Aperture circular with a moderately strong 

 angulation at the posterior angle; peristome simple; outer lip thin, 

 slightly expanded and slightly reflected ; inner lip moderately thick- 

 ened. The parietal wall is covered by a heavy callus, which is 

 strongly separated from the preceding turn and renders the peritreme 

 complete. 



The specimen described and figured, U.S.N.M. No. 307432, was 

 received from Sowerby and Fulton with the designation "New 

 Grenada" (Colombia). It has 4.4 whorls and measures: Height, 

 18.7 mm.; greater diameter, 27.7 mm.; lesser diameter, 20.2 mm. 

 Height of aperture, 11 mm. ; diameter, 12.8 mm. 



Da Costa's figure yields the following measurements : Height, 21.1 

 mm. ; greater diameter, 33.5 mm. ; lesser diameter, 24.7 mm. Height 

 of aperture, 13.4 mm.; diameter, 14.9 mm. It has 5 whorls. 



This species recalls A. {A.) caucaense (Da Costa) but lacks the 

 basal sinus or configuration described therefor. It also suggests 

 A. {A.) 'perezi (Hildalgo), but is much larger than that species. 



APEROSTOMA (APEROSTOMA) PEREZI (Hidalgo) 



Plate 38, Figures 4-6 



1866. Cyclotus perezi Hildago, Journ. Conchyl., vol. 14, p. 344, pi. 14, fig, 2. 

 1897. Neocyclotus (Neocyclotus) perezi Kobelt and Moixendorff, Nachrb. 



deutschen malak. Ges., vol. 29, p. 137. 

 1923. Poteria {Neocyclotus) perezi H. B. Baker, Occ. Pap. Mus. Zool. Univ. 



Michigan, No. 137, p. 43. 



Shell small, depressed-helicoid, the upper surface bright reddish 

 chestnut-brown. There is a very inconspicuous, narrow, slightly 

 lighter zone immediately above the periphery. The base has a 

 broad dull chestnut-brown band immediately below the periphery 

 and another narrow one of the same shade on the middle of the 

 base. The rest is a little paler than the upper surface. The nucleus 

 consists of 2 moderately large, well-rounded, smooth turns. The 

 postnuclear whorls are inflated, strongly rounded, almost flattened 

 at the summit. The summit of the last one falls slightly below 

 the periphery of the preceding turn. The postnuclear whorls are 

 marked by regular fine riblets. Suture strongly constricted. Pe- 

 riphery well rounded. Base openly umbilicated and marked by 

 the continuation of the axial riblets, which become a little less 



