THE CYCLOPHORID LAND MOLLTJSIKS OF AMERICA 191 



APEROSTOMA (INCIDOSTOMA) PICHINCHENSE, new species 



Plate 26, Fjguees 10-12 



Shell large, helicoid. The early whorls denuded of periostracum 

 livid white; on the last one the periostracum is olivaceous with a 

 brownish tinge on the upper surface. There is a narrow white periph- 

 eral zone, and the base is pale chestnut with an olivaceous tinge ; inte- 

 rior of aperture bluish white. The nucleus consists of 2 small rounded, 

 smooth turns. The postnuclear whorls are well rounded, slightly 

 inbent at the suture on the last turn and marked by decidedly retrac- 

 tively curved axial riblets, which become decidedly irregular in 

 strength and spacing on the last whorl. On this there are also 

 oblique malleations resembling scratches. Suture strongly impressed. 

 Periphery feebly angulated. Base openly umbilicated, inflated, 

 strongly rounded, and marked by the continuation of the axial rib- 

 lets, which become gradually intensified on the umbilical wall. Ap- 

 erture circular, excepting the siphonlike projection at the posterior 

 angle; peristome slightly thickened and reflected on the inner lip; 

 thin on the outer, where it is produced at the posterior angle to form 

 an incomplete siphon, separated there by a narrow slit. The parie- 

 tal wall is covered with a thick callus. The peristome is rendered 

 incomplete by the sinus at the posterior angle. Operculum typically 

 aperostomid having about 9 whorls. 



The type, U.S.N.M. No. 316109, comes from Quito, Ecuador. It has 

 5 whorls and measures : Height, 26.6 mm. ; greater diameter, 47.6 mm. ; 

 lesser diameter, 35.1 mm. Height, of aperture, 16.2 mm.; diameter, 

 20.6 mm. 



This species is readily distinguished from A. (/.) malleatum by its 

 more elevated spire and less strongly malleated sculpture. 



APEROSTOMA (INCIDOSTOMA) HEDUI, new species 



Plate 26, Figures 1-3 



1863. Cyclotus incomptus Reeve, Conchologia iconica, vol. 14, sp. 8 (not Cyclo- 

 stoma incomptum Sowerby, Thesaurus conchyliorum, vol. 1, SuppL, 

 p. 160*. 1850) . 



Shell decidedly depressed-helicoid, almost planorbid; extreme tip 

 reddish brown, the succeeding whorls pale brown, the last whorl chest- 

 nut-brown on the upper surface and dark chestnut-brown on the 

 lower, with a narrow pale-brown peripheral zone. The nucleus 

 consists of 2 small, well-rounded, smooth turns. The postnuclear 

 whorls are marked by decidedly retractively curved axial riblets, 

 which become much enfeebled on the last whorl, where they are 

 merely indicated. Suture very strongly impressed, narrowly chan- 

 neled. The last whorl is slightly decurrent near the aperture. 

 Periphery feebly angulated. Base openly umbilicated, well rounded, 



