THE CYOLOPHORID LAND MOLLUiSKS OF AMEKTOA 251 



The specimen described and figured, U.S.N.M. No. 307446, comes 

 from Quito, Ecuador. It has 4.6 whorls and measures: Height, 20.8 

 mm. ; greater diameter, 36.9 mm. ; lesser diameter, 24.2 mm. Height 

 of aperture, 14 mm. ; diameter, 18.2 mm. 



U.S.N.M. No. 307396 contains three topotypes collected by Cum- 

 ing; U.S.N.M. No. 307431 contains another topotype from the Morelet 

 collection. 



This species is easily differentiated from A. (A.) ecitadorense and 

 subcingulatum (Kobelt) by its smoother surface and much larger 

 aperture. 



APEROSTOMA (APEROSTOMA) OLIVACEUM, new species 

 PliATE 36, FiGXJEES 10-12 



Shell low, helicoid, the early whorls pinkish, the last olivaceous 

 with darker axial streaks, which are of irregular width and spacing. 

 There is a light zone immediately above the periphery and a darker 

 broad zone covering the posterior two-fifths of the base. The 

 umbilical wall and the rest of the base are of the same color as the 

 upper surface of the last turn ; interior of the aparture bluish. The 

 nucleus consists of 2 small, well-rounded, smooth turns. The post- 

 nuclear whorls are well rounded; however, there is a depressed area 

 a little below the summit. The postnuclear whorls are marked by 

 retractively curved axial ribs, which are of about the same width 

 as the spaces that separate them and which grow consecutively 

 stronger as the shell increases in size. In addition, there are irregu- 

 lar, oblique scratches in the depressed area below the summit on 

 the last turn and feeble indications of spiral markings on the rest 

 of the last whorl. Suture strongly impressed. The periphery is 

 well romided. The light band, however, gives it the optical illusion 

 of being angulated. Base narrowly umbilicated, inflated, strongly 

 rounded, and marked by the continuaaion of the axial ribs, which 

 become slightly stronger on the umbilical wall. Aperture very 

 large, subcircular ; peristome simple ; outer lip thin ; inner thickened. 

 The parietal wall is covered by a very heavy callus which is slightly 

 emarginated, and which renders the peritreme complete. 



The type, U.S.N.M. No. 524084, comes from Ecuador. It has 4.6 

 whorls and measures : Height, 20.8 mm. ; greater diameter, 34.2 mm. ; 

 lesser diameter, 23.1 mm. Height of aperture, 13.9 mm.; diameter, 

 16.6 mm. 



U.S.N.M. No. 307423 contains a topotype. 



This species in form and sculpture most nearly resembles A. {A.) 

 castanewm^ from which its much paler coloration easily distinguishes it. 



