138 BTILLtEITIlN 181, UNlT'EiD SfTATEiS NlATTOOSIlAiL MUS1E:UM 



gestion of the angle at the outer edge of the umbilicus present. 

 Aperture circular; peristome thin. Operculum? 



The type, U.S.N.M. No. 115717, was collected by John B. Hender- 

 son in the marl stratum of the Bowden Beds, Miocene, in St. Thomas 

 Parish, Jamaica. It has 3.4 whorls remaining and measures: 

 Height, 16.3 mm.; greater diameter, 30,0 mm.; lesser diameter, 

 20.0 mm. 



The peculiar sculpture combined with the absence of the umbilical 

 keel separates this species from all the other known Jamaican 

 cyclophorids. 



INCERTICYCLUS BOWDENENSIS, new species 

 Plate 41, Figtjbes 4-6 



Shell small, helicoid, yellowish white. Nuclear whorls decollated. 

 The early postnuclear whorls somewhat impressed at the summit; 

 t le last appressed. The early whorls are marked by slender, hairlike 

 incremental lines. Beginning with the last half of the penultimate 

 turn, decidedly obliquely protractively slanting axial rugae make their 

 appearance. They take a sudden retractive slant near the summit 

 where they are weaker and less regular. Periphery rounded. Base 

 strongly rounded, openly umbilicated, and marked by lines of growth 

 only. A rather strong, somewhat notched, moderately broad keel 

 forms the outer edge of the umbilicus, while the umbilical wall is 

 marked by riblike gatherings of the incremental lines. Aperture 

 circular, oblique; peristome simple, thickened to form an auricle at 

 the posterior angle. 



The type, Acad. Nat. Sci. Philadelphia No. 82532a, was collected 

 by Uselma C. Smith and S. L. Schermo in the Miocene formation 

 at Bowden, Jamaica. It has 3.5 whorls remaining and measures: 

 Height, 10.8 mm. ; greater diameter, 15.7 mm. ; lesser diameter, 12 mm. 



Its lesser size and comparatively weak sculpture will readily 

 distinguish it from Incerticyclus hdkeri (Simpson) and /. schermoL 



INCERTICYCLUS SCHERMOI. new species 

 Pl.\te 41, Figtjbes 10-12 



Shell of medium size, helicoid, cream yellow. Nuclear whorls 1.5, 

 small, well rounded, smooth. Postnuclear whorls well rounded; all 

 but the last turn marked by very strong, slightly retractively curved 

 axial riblets, which are less than half as wide as the spaces separating 

 them. The last whorl is very roughly wrinkled. The axial ribs 

 persist and are even stronger than on the preceding whorls, but they 

 are rendered irregular by decidedly obliquely protractively slanting 

 folds. The latter are not quite so broad as the spaces separating 



