264 BULLETIN 181, UNITED STATES NATIONAL MUSEUM 



what inbent. The summit of the last turn gradually falls below the 

 periphery of the preceding turn at the aperture, and is more than 

 the width of the brown band below the brown band. The postnu- 

 clear whorls are marked by feeble axial riblets, which are merely 

 indicated on the last half of the last turn. Suture very deeply im- 

 pressed. Base broadly openly umbilicated, somewhat inflated, well 

 rounded and marked by the continuation of the axial ribs, which do 

 not become intensified on the umbilical wall. Aperture very large; 

 peristome simple; outer lip expanded and slightly reflected; inner 

 lip slightly thickened. A very heavy callus covers the parietal wall, 

 from which it is separated by a strongly impressed groove, which 

 renders the peritreme complete. Operculum typically aperostomid, 

 showing 9 whorls. 



The type, U.S.N.M. No. 524125, comes from Brazil. It has 4.3 

 whorls and measures : Height, 12.1 mm. ; greater diameter, 22.1 mm. ; 

 lesser diameter, 15 mm. Height of aperture, 6.9 mm.; diameter, 

 10.5 mm. 



The pale coloration, obsolete supraperipheral light zone, and feeble 

 axial sculpture on the umbilical wall readily differentiate this species 

 from A. (A.) merrilli. 



APEROSTOMA (APEROSTOMA) POPAYANUM (Lea) 



Plate 39, Figuees 17-19 (type), 20-22 



1839. Cyclostoma popayana Lea, Trans. Amer. Phil. Soc, new ser., vol. 6, p. 94, 



pi. 23, fig. 76. 

 1847. Aperostoma popayanum Pfeifj<kk, Zeitsch. f. Malak., vol. 4, p. 104. 

 1852. Cyclotus popaynnus Pfeiffer, Monographia pneumonopomorum viventiura, 



vol. 1, p. 21. 

 1897. Neocyclotus (Neocyclotus) popayanus Kobbxt and Mollendorff, Nachrb. 



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

 1923. Poteria (Neocyclotus) popayana H. B. Bakek, Occ. Pap. Mus. Zool. Univ. 



Michigan, No. 137, p. 44. 



Shell helicoid, the upper surface olivaceous horn colored with axial 

 streaks of darker shades, which are of irregular size and spacing. 

 There is a narrow light zone immediately above the periphery and 

 a brownish olivaceous band below the periphery, which gradually 

 fades basally. The rest of the base is horn colored. The nucleus 

 consists of 2 small, well-rounded, smooth turns, forming a rather 

 elevated spire. The postnuclear whorls are well rounded; the last 

 one slightly deflected below the periphery, forming a weak cord at 

 the appressed summit, below which there is an impressed groove. 

 The postnuclear whorls are marked by retractively curved slender 

 axial riblets, which are narrower than the spaces that separate them, 

 and which on the last turn become rather irregular. Here, too, there 

 are oblique scratches in the depressed area below the summit and, to 



