202 BULLETTN 181, UNITED SOlATEiS NATlONlAL MtTSETIM 



marked by numerous short rugae on the flattened portion of the sum- 

 mit, while the rest bear the usual retractive and protractive riblets re- 

 sulting in the granulations characteristic of the group. Suture well 

 impressed. Periphery obscurely angulated. Base narrowly um- 

 bilicated, inflated, and marked by the granular sculpture characteristic 

 of the spire, which extends slightly over the umbilical edge but does 

 not cover all of the umbilical wall. Aperture circular, with a slight 

 angulation at the posterior angle ; peristome simple, the inner slightly 

 thickened and reflected ; the outer sharp. The parietal wall is covered 

 by a thin callus. 



The type, U.S.N.M. No. 339947, was collected by H. Pittier at 

 Guaremales, Venezuela. It has 4.2 whorls and measures : Height, 13.4 

 mm. ; greater diameter, 18.0 mm. ; lesser diameter, 13.3 mm. Height of 

 aperture, 9.3 mm. ; diameter, 8.8 mm. 



The small size readily distinguishes this species from others of the 

 subgenus except A. (A.) hurrlngtoni, which is still smaller. 



APEROSTOMA (AUSTROCYCLOTUS) BURRINGTONI, new species 



Plate 28, Figure® 16-18 



1923. Poteria (Neocyclotus) granadensis rugata H. B. Baker, Occ. Pap. Mus. 

 Zool. Univ. Michigan, No. 137, pp. 36-37, pi. 5, figs. P, Q. 



Shell very small, helicoid. Nuclear whorls pale reddish brown, the 

 rest of the shell gradually fading to straw color on the last turn. The 

 nucleus consists of 1.5 small, well-rounded, smooth turns; the post- 

 nuclear whorls are strongly rounded, somewhat flattened near the 

 suture, and marked by rather regular axial riblets near the suture, 

 which become wavy anteriorly, where they assume the granular sculp- 

 ture characteristic of the gi'oup. Suture well impressed on the early 

 whorls, less so on the last. Periphery well rounded. Base narrowly 

 umbilicated, inflated, rounded, marked by the same type of sculpture 

 as that which characterizes the spire. This, however, becomes en- 

 feebled toward the umbilicus, which is free of granulation. Aperture 

 circular, slightly angulated at the posterior angle ; peristome simple ; 

 that of the inner lip somewhat thickened and reflected ; the outer sharp. 

 Operculum typically aperostomid, of about 4 whorls. 



The type, Acad. Nat. Sci. Philadelphia No. 104625, is one of four 

 specimens collected by S. Brown at Cariaquita, Venezuela. It has 3.9 

 whorls and measures: Height, 9.8 mm.; greater diameter, 13.4 mm.; 

 lesser diameter, 9.7 mm. Height of aperture, 6.6 mm.; diameter, 

 6.3 mm. 



The very small size of this species easily distinguishes it from all the 

 other Aitstrocyclotus. 



