230 BULLETIN 181, UNITEID STATE® NATIOINIAIL MUSEfUM 



APEROSTOMA (APEROSTOMA) ALLANTAYUM, new species 

 Plate 32, Figubes 4-6 



Shell of medium size, very depressed-helicoid ; the early denuded 

 whorls are soiled flesh colored; the succeeding turns dark straw 

 colored with an orange flush, the last reddish chestnut-brown with 

 a narrow light zone immediately above the narrow dark band at 

 tlie periphery; posterior half of the base a little darker than the 

 upper surface, while the anterior is considerably paler; interior of 

 aperture bluish white. The nucleus consists of about 2 small, well- 

 rounded, smooth turns; the postnuclear whorls are moderately well 

 rounded, all but the last marked by very regular, retractively slanting 

 axial riblets, which are about as wide as the spaces that separate 

 them. On the last whorl these become much enfeebled and reduced 

 to irregular lines of growth. Here, too, we have slight indications 

 of malleations. The last whorl is slightly decurrent on the last 

 quarter of a turn. Suture well impressed. Periphery feebly ob- 

 soletely angulated. Base openly umbilicated, inflated, well rounded 

 and marked by irregular, wavy, strong incremental lines, which are 

 developed into irregular ribs on the umbilical wall. Aperture de- 

 cidedly oblique, very broadly tear-shaped, with a pronounced drawn- 

 out angulation at the posterior angle, which has a groove in its 

 middle on the inside; peristome simple; the outer lip thin; the 

 inner somewhat thickened. The parietal wall is covered by a thick 

 callus which renders the peritreme complete. 



The type, U.S.N.M. No. 524046, comes from the Eich collection 

 and is labeled "Peru." It has 4.4 whorls and measures: Height, 

 17.4 mm.; greater diameter, 30.3 mm.; lesser diameter, 21.2 mm. 

 Height of aperture, 11.7 mm. ; diameter, 13.9 mm. 



U.S.N.M. No. 22203 contains another specimen received from Mac- 

 Andrew labeled "Peru." 



The conspicuous bicolored base readily distinguishes this from the 

 other feebly malleated members of this group. 



THE GROUP OF APEROSTOMA (APEROSTOMA) DUNKERI 

 Umbilical wall strongly distinctly axially ribbed. 



APEROSTOMA (APEROSTOMA) DUNKERI (Pfeiffer) 



Plate 32, Figures 1-3 



1856. Cyclotus dunkeri Pfeitfee, Malak. Blatter, vol. 3, p. 256. 



1864. Cyclotus dunkeri Reeve, Conchologia iconica, vol. 14, pi. 2, sp. 9. 



1897. Neocyclotus (Neocyclotus) dunkeri Kobelt and Mollendobff, Nachrb. 



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

 1923. Poteria (Neocyclotus) dunkeri H. B. Bakeb, Occ. Pap. Mus. Zool. Univ. 



Michigan, No. 137, pp. 39, 40, 43. 



