256 BULLETIN 181, UNITED STATES NATIONAL MUSEUIM 



The type, U.S.N.M. No 206494, was collected by Gabaldon and 

 sons at an altitude of 8,400 ft., in the Sierra Nevada Mountains, 

 Venezuela. It has 4.3 whorls and measures: Height, 15.8 mm.; 

 greater diameter, 28.5 mm.; lesser diameter, 19.3 mm. Height of 

 aperture, 10.9 mm. ; diameter, 13 mm. 



The rough irregular sculpture and weakly impressed suture will 

 readily differentiate this species from A. (A.) agassizi. 



THE GROUP OF APEROSTOMA (APEROSTOMA) FASCIATUM 



Small shells with rather narrow umbilicus and small aperture. 



APEROSTOMA (APEROSTOMA) FASCIATUM (Kobelt) 



Plate 37, Figures 7-9 



1912. Neocyclotus popayanus fasciata Kobext, Martini-Chemnitz Conchylien 

 Cabinet, vol. 1, sect. 19, pt. 3, p. 900 (pi. 7, figs. 7-10), pi. 139, figs. 1-5. 



1923. Poteria (Neocyclotus) popayana fasciata H. B. Bakeb, Occ. Pap. Mus. Zool. 

 Univ. Michigan, No. 137, 40, 44. 



1923. Poteria (Neocyclotvs) dunkeri var. approaching P. popayana H. B. Baker, 

 Occ. Pap. Mus. Zool. Univ. Michigan, No. 137, pp. 40, 45, pi. 5, fig. T. 



Shell small, helicoid, covered with an olivaceous-brown periostracum, 

 which fades to olivaceous on the last portion of the last turn. In 

 addition, there is a pale band immediately above the periphery and in- 

 dications of additional inconspicuous spiral lighter zones on the upper 

 surface. There is a dark band of brown about one-fifth width of base 

 immediately anterior to the periphery and in addition to that lesser 

 spiral bands of brown on the anterior half of the base; the rest is 

 olivaceous horn colored ; the interior of aperture is bluish white. The 

 nucleus consists of 2 moderately large, well-rounded, smooth turns. 

 The postnuclear whorls are well elevated, inflated, and strongly 

 rounded. The last one is deflected below the periphery for almost a 

 turn. The postnuclear whorls are marked by feeble, retractively 

 curved, hairlike riblets, which become much enfeebled on the last 

 quarter of the last turn. Suture strongly impressed. Periphery well 

 rounded. Base narrowly umbilicated, inflated, well rounded and 

 marked by the feeble continuation of the axial ribs on the posterior 

 half; on the anterior half and the umbilical wall the axial ribs become 

 very much intensified. Aperture rather small, circular, with a slight 

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

 slightly flaringly expanded ; the inner somewhat thickened. A mod- 

 erately thick callus covers the parietal wall. It is separated from the 

 preceding turn by an impressed line and renders the peritreme com- 

 plete. Operculum typically aperostomid, showing 9 whorls. 



The specimen described and figured is one of two, U.S.N.M. No. 

 57766, which comes from Puerto Cabello, Venezuela. It has 4.3 



