THE CYCL.0PHORID LAKD MOLLUSKS OF AMEiR'ICL\ 233 



covered by a thick callus, which renders the peritreme complete. The 

 operculum is tj^pically aperostomid, having 10 whorls. 



The type, U.S.N.M. No. 524047, was collected by H. Pittier in the 

 Rio Paez Valley, Colombia, at an elevation of 2,500 meters. It has 

 4.7 whorls and measures: Height, 18.7 mm.; greater diameter, 33.1 

 mm.; lesser diameter, 22.2 mm. Height of aperture, 12.8 mm.; 

 diameter, 15.6 mm. 



Its smaller size will readily differentiate this from A. (A.) dunheri 

 (Pfeiifer). 



GROUP OF APEROSTOMA (APEROSTOMA) CARMIOLI 



Umbilical wall closely finely axially ribbed. 



APEROSTOMA (APEROSTOMA) CARMIOLI, new species 



Plate 32, Figures 19-21 



Shell large, helicoid; the early turns reddish; the later covered on 

 the upper surface by a golden-yellow periostracum. There is a light 

 zone immediately above the periphery, while the posterior half of the 

 base is chestnut brown; the rest is of the same color as the upper 

 surface; interior of aperture bluish white. The nucleus consists of 

 2 small, well-rounded, smooth turns; the postnuclear whorls are in- 

 flated, strongly rounded, and marked on the upper surface by very 

 weak, retractively curved, flattened riblets, which become evanescent 

 on the last whorl. Suture strongly impressed. Periphery well 

 rounded. Base openly umbilicated, inflated, well rounded, and 

 marked by the continuation of the axial ribs, which gain in intensity 

 below the middle and become stronger on the umbilical wall, where 

 they form distinct fine ribs, which are not quite as wide as the spaces 

 that separate them. The last whorl is slightly decurrent near the 

 peristome. Aperture large, broadly oval with a conspicuous angle 

 at the posterior angle, which has a groove in the middle; peristome 

 simple ; the outer lip thin. The basal lip bears 2 notches ; the inner 

 lip is somewhat thickened, while the parietal wall is covered with a 

 moderately thick callus, which renders the peritreme complete. 



The type, U.S.N.M. No. 25034, was collected by Carmiol in Costa 

 Eica, It has 4.9 whorls and measures: Height, 27.2 mm.; greater 

 diameter, 40.4 mm.; lesser diameter, 29.4 mm. Height of aperture, 

 16.5 mm.; diameter, 19 mm. 



U.S.N.M. No. 405227 contains a young specimen collected by M. 

 Valerio at Chitaria, Costa Rica. 



This species differs from the other members of this group by being 

 considerably larger. 



