THE CYOLOPHORID LAND MOI/LU&Kg OF AMERTOA 263 



The small size and pale coloration readily distinguish this species 

 from the other members of the group. 



APEROSTOMA (APEROSTOMA) MERRILLI, new species 



Plate 38, Figures 19-21 



Shell low, helicoid. The upper surface olivaceous, with a brownish 

 tinge. There is a broad light zone immediately above the periphery 

 and a broad dark zone covering about two-fifths of the base immedi- 

 ately below the periphery. The rest of the base is a little paler than 

 the upper surface. The nucleus consists of 2 small, well-rounded, 

 smooth turns. The post nuclear whorls are strongly rounded. The 

 last one is gradually deflected until it falls about halfway across the 

 dark subperipheral band at the aperture. The postnuclear whorls 

 are marked by retractively curved, slender axial riblets, which are 

 not quite as wide as the spaces that separate them. These riblets be- 

 come somewhat confused and irregular on the last half of the last 

 turn. Suture strongly impressed. Periphery obscurely angulated. 

 Base openly, rather broadly umbilicated, inflated, strongly rounded, 

 and marked by the continuation of the axial riblets, which become 

 obsolete on the umbilical wall. Aperture almost circular with a 

 slight angulation at the posterior angle ; peristome simple ; outer lip 

 thin; inner slightly thickened. The parietal wall is covered by a 

 moderately thick callus which renders the peritreme complete. 



The type, U.S.N.M. No. 58310 comes from Brazil. It has 4.3 

 whorls and measures : Height, 14.6 mm. ; greater diameter, 23.7 mm, ; 

 lesser diameter, 17 mm. Height of aperature, 9.5 mm.; diameter, 

 10.9 mm. 



U.S.N.M. No. 203708 contains five not quite perfect specimens ob- 

 tained by H. B. Merrill on the Braganza Railway in the Amazon 

 Valley; U.S.N.M. No. 57286 contains another specimen obtained by 

 the Agassiz Expedition to Brazil. 



The larger size, darker coloration, and the feeble sculpture on the 

 umbilical wall readily distinguish this species from A. (A.) nanum. 



APEROSTOMA (APEROSTOMA) PULCHELLUM, new species 



Plate 38, Figures 16-18 



Shell small, depressed-helicoid, thin. The early whorls with a 

 pinkish tinge ; the later pale horn colored. There is an inconspicuous 

 light zone immediately above the periphery and a moderately broad 

 chestnut band immediately below it. The rest of the base is colored 

 like the upper surface of the last whorl. The nucleus consists of 2 

 rather large, well-rounded, smooth turns. The postnuclear whorls 

 are well rounded, slightly flattened toward the summit, or even some- 



