THE CYCLOPHORI'D LAKTD MOLLUSIKS OF AMERICA 139 



them. Periphery well rounded. Base strongly rounded, openly um- 

 bilicated with a very strong keel at the outer edge of the umbilicus. 

 Deep pits are present at the keel, which extend as impressed grooves 

 over the anterior third of the base. Anterior €o the keel the umbil- 

 ical wall is also deeply pitted and the impressed areas extending 

 from the pits over the umbilical wall let the intermediate space appear 

 as ribs marked by incremental lines. Aperture oblique, circular. 



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

 by Usehna C. Smith and S. L. Schermo in the Miocene beds at 

 Bowden, Jamaica. It has 4.4 whorls and measures : Height,, 13 mm. ; 

 greater diameter, 19.8 mm.; lesser diameter, 15.3 mm. Thirteen 

 young and fragmentary specimens are registered under the same 

 number. 



The strong basal sculpture readily differentiates this from Iiwer- 

 ticyclm howdenemis and the strong spiral keel at the umbilicus sepa- 

 rates it from Incerticyclus haheri (Simpson). 



INCERTICYCLUS PEKPALLIDUS (C. B. Adams) 



Plate 18, Figubes 4-6 



1852. Cyclostoma perpallidum C. B. Adams, Ann. Lye. Nat. Hist. New York, 



vol. 5, p. 81. 

 1852. Cyclotus perpallidus Pfeiffer, Monographia pneumonopomoriun viventium, 



vol. 1, p. 29. 

 1857. Cyclostoma perpallidus Chitty, Proc. Zool. Sec London, vol. 25, p. 157. 

 1898. Neocyclotus (Plectocyclotus) perpallidus Kobelt and Mollendoeff, Nachrb. 



deutschen malak. Ges., vol. 9, p. 138, reprint. 



Shell of medium size with sides sloping regularly to the spire, 

 soiled white. The nucleus consists of 1.5 smooth, well-rounded turns. 

 The postnuclear whorls are moderately well rounded, the first marked 

 by feeble retractively curved axial riblets. Beginning with the 

 second, fine wavy axial wrinkles make their appearance. These 

 wrinkles branch and anastomose, enclosing spaces between them of 

 varying length. They are a little weaker toward the summit than 

 on the major portion of the whorls. Suture moderately well im- 

 pressed on all of the turns. Periphery obscurely angulated and 

 marked like the spire. Base very moderately rounded, almost flat- 

 tened, marked by the continuation of the axial wrinkles, which here 

 are retractively slanting and marked near the umbilicus by strong 

 coarse ribs, which are wider than the spaces that separate them. The 

 umbilical wall is marked by the continuation of these ribs and fine 

 incremental lines. There is only the merest indication of angulation 

 at the outer edge of the umbilicus. Aperture subcircular, decidedly 

 protracted into a claw at the posterior angle, having the outer lip 

 thin, inner somewhat thickened. Operculum? 



