THE CYOLOPHORID LAND M0I«LUSiK9 OF AMEiRTClA 269 



APEROSTOMA (CYCLOHIDALGOA) BELLI HAUGHTI, new subspecies 

 PlATE 30, FIGUBES 24-26 



Shell very large, helicoid, covered with a chestnut-brown perios- 

 tracum. The nucleus consists of 2 moderately large, well-rounded, 

 smooth turns. The postnuclear whorls are strongly rounded, ap- 

 pressed at the summit, with a depressed zone a little anterior to the 

 simunit and marked by somewhat sinuous, retractively curved, closely 

 spaced, slender axial ribs which are about as wide as the spaces that 

 separate them. These riblets become enfeebled on the last portion of 

 the last turn. Suture strongly impressed. Periphery inflated, well 

 rounded. Base narrowly umbilicated, inflated, strongly rounded, and 

 marked by the same type of sculpture as that which characterizes the 

 upper surface. This also extends over the umbilical wall. Aperture 

 large, circular, with a moderately strong auricle at the posterior 

 angle; peristome simple; outer lip thin; inner lip thickened. The 

 parietal wall is covered by a thick callus, which renders the peritreme 

 complete. The operculum is typically aperostomid, showmg 6 whorls. 



The type, U.S.N.M. No. 524136, was collected by Oscar Haught at 

 the south part of the Department of Santander, Colombia. It has 

 5.1 whorls and measures: Height, 30.2 mm.; greater diameter, 43 

 mm.; lesser diameter, 30.3 mm. Height of aperture, 22.8 mm.; 

 diameter, 22.2 mm. 



U.S.N.M. No, 472798 contains eight topotypes from the same source. 



Its smaller size will differentiate it from A. (0.) helU belli 

 (Beddome). 



APEROSTOMA (CYCLOHIDALGOA) TRANSLUCIDUM (Sowerby) 



Shell of helicoid shape. Nuclear whorls 2, strongly rounded, 

 smooth. Postnuclear whorls strongly rounded and marked by 

 numerous closely crowded axial riblets. Suture well impressed. 

 Periphery inflated, strongly rounded. Base narrowly umbilicated, 

 inflated, strongly rounded, and marked like the spire. Aperture cir- 

 cular; peristome simple. Operculum typically aperostomid. 



KEY TO THE SUBSPECIES OF APEROSTOMA (CYCLOHmALGOA) TRANSLUCIDUM 



Greater diameter more than 26 mm major 



Greater diameter less than 23 mm. 

 Spire strongly elevated. 



Greater diameter more than 18 mm. 



Axial riblets coarse bejumense 



Axial riblets not coarse trinitense 



Greater diameter less than 13 mm pygmaeum 



Spire not strongly elevated. 



Greater diameter more than 22 mm translucidum 



Greater diameter less than 16 mm dunoonense 



428349 — 42 18 



