THE CYCfLOPHORID LAND MOLrLUSKS OF AMERICA 265 



a lesser extent, on the rest of the whorl. Periphery obscurely angu- 

 lated. Base narrowly umbilicated, and marked by the feeble con- 

 tmuation of the axial ribs, which do not become intensified on the 

 umbilical wall. Aperture circular with a conspicuous angulation at 

 tlie posterior angle; peristome simple; outer lip thin, somewhat ex- 

 panded and slightly reflected on the basal half; slightly thickened on 

 the inner lip with the parietal wall covered by a moderately thick 

 callus which is separated from the preceding turn by an impressed 

 line, which renders the peritreme complete. Operculum typically 

 aperostomid, showing 9 whorls. 



Lea's type, U.S.N.M. No. 104453, was collected by Dr. Gibbons near 

 Popayan, Grenada (that is, southwest Colombia). It has 4.2 whorls 

 and measures: Height, 14.7 mm.; greater diameter, 22.6 mm,; lesser 

 diameter, 16 mm. Height of aperture, 9.8 mm. ; diameter, 10.7 mm. 



A second specimen with the type and bearing the same number 

 is considerably larger but in every way similar to the dead denuded 

 type. It measures: Height, 18.4 mm.; greater diameter, 27.5 mm.; 

 lesser diameter, 19 mm. Height of aperture, 10.8 mm.; diameter, 

 12.6 mm. It has 4.6 whorls. 



We have also figured one of two specimens received from Bland, 

 U.S.N.M. No. 307406, collected at Marmato, New Grenada (south- 

 western Colombia). It has 4.4 whorls and measures: Height, 15.4 

 mm.; greater diameter, 23.5 mm.; lesser diameter, 17 mm. Height 

 of aperture, 10.4 mm. ; diameter, 10.8 mm. 



U.S.N.M. No. 356029 contains two young specimens from New 

 Grenada. 



This species appears nearest related to ^. (A.) balsasense, from 

 which it can readily be differentiated by the scratched surface of the 

 last whorl, which is not present in halsasense. 



APEROSTOMA (APEROSTOMA) BALSASENSE, new species 



Plate 39, FiGtrBEs 1-3 



Shell depressed-helicoid. The early whorls are flesh colored; the 

 last two horn colored with a brownish flush. There is a very narrow 

 light zone immediately above the periphery and a broad dark zone 

 below the periphery which extends from the periphery to almost the 

 middle of the base, gradually fading anteriorly. The anterior portion 

 and umbilical wall are horn colored; the interior of the aperture is 

 flesh white and shows the external banding. The nucleus consists of 

 2 small, well-rounded, smooth turns. The postnuclear whorls are well 

 rounded, appressed at the summit and marked on the penultimate 

 whorl by very regular and regularly spaced retractively curved axial 

 ribs. These ribs are about as wide as the spaces that separate them. 

 On the last whorl the riblets become somewhat irregular and toward 



