THE CYCLOPHORlID LAND MOLLUSIKS OF AMEIRIOA 193 



is from the J. B. Henderson collection; it bears no locality data. 

 Sowerby's specimen, which he states is in Mr. Cuming's collection, 

 is also without locality mention. 



APEROSTOMA (INCIDOSTOMA) PIZARROI, new species 

 Plate 26, Figukes 7-9 



Shell depressed-helicoid, chestnut-brown on the upper surface, with 

 a narrow pale-yellow zone immediately above the periphery, while 

 below the periphery there is a broad, very dark chestnut-brown band, 

 which extends over two-fifths of the width of the base. Anterior 

 to this and on the umbilical wall the shell is straw colored with a 

 brownish flush and irregular zones of white. The nucleus consists 

 of 1.6 small, well-rounded smooth turns. The postnuclear whorls 

 are well rounded, the last one slightly flattened near the suture. 

 The postnuclear whorls are marked by fine, closely spaced, retractively 

 curved axial ribs, which are not quite as wide as the spaces that 

 separate them. These riblets are very regular in strength and spac- 

 ing. Suture rendered inconspicuous by the appressed whorl. Periph- 

 ery well rounded, rendered angulated in appearance by the light 

 peripheral zone. This, however, is an optical illusion. Base openly 

 umbilicated, marked by the continuation of the axial riblets, which 

 become strengthened on the umbilical wall. Aperture subcircular, 

 produced into a weak auricle at the posterior angle ; peristome simple, 

 a little thicker on the inner lip than on the outer. Parietal wall 

 covered by a thick callus. In this species the peristone is produced 

 into an auricle constituting a slight channel. Operculum typically 

 aperostomid, having 7 whorls. 



The type, U.S.N.M. No. 20109, was collected by the Wilkes Explor- 

 ing Expedition at Maguas, Peru. It has 4.4 whorls and measures: 

 Height, 19.9 mm.; greater diameter, 37.4 mm.; lesser diameter, 26 

 mm. Height of aperture, 13.3 mm.; diameter, 17.3 mm. 



U.S.N.M. No. 36942 contains two additional specimens from the 

 same source. 



The large aperture readily distinguishes this species from A. (/.) 

 nirafe. 



APEROSTOMA (INCIDOSTOMA) NIRAFE, new species 

 Plate 27, Figubes 23-25 



Shell of medium size, depressed-helicoid, covered with a chestnut- 

 brown periostracum on the upper surface. There is a very broad 

 darker band immediately anterior to the periphery, which gradually 

 fades into the basal color scheme. The nucleus consists of a little 

 more than 2 small, well-rounded smooth whorls. The postnuclear 

 whorls are well rounded, curving downward toward the suture and 



