CERION, GROUP X. 247 



between strong, slightly curved ribs, separated by two or three times 

 their width or sometimes irregularly and widely spaced on the cylin- 

 drical portion, which consists of 3 to 4 whorls; those above forming 

 a short cone on which the ribs are much closer. Whorls li^, flat, 

 the last ascending, somewhat tapering downward, but with well 

 rounded base, upon which the ribs are obsolete, but replaced by 

 wrinkles or fine costulae. Umbilical rima very deep, curved, the 

 area below it wide, usually bounded by a spiral groove well within 

 the basal margin of umbilical tract. Aperture ovate-truncate, brown 

 in the throat; parietal lamella very strong, often calloused on the left 

 side; rather short; axial lamella small, one whorl long. "Peristome 

 stout, white, broadly reflexed, its face convexly thickened but not 

 "duplicate;" broadly vaulted over the open and dilated umbilical 

 area; parietal callus varying from thin to heavy, but always thin at 

 the edge. 



Length 35, diam. 13 mill. 



Length 341, diam. 14^ mill. 



Length 34-J, diam. 15^. 



Bahamas: Abaco (R. Swift% 



O. (Maynardia) maynardi P. and V., Proc. A. N. S. P. 1895, p. 

 210; 1896, p. 323, pi. 11, f. 31. 



This form differs from C. abacoense in the coarser, more widely 

 spaced ribs, deeper umbilical chink and larger umbilical area. 



A series of 30 specimens (No. 73628), received without locality^ 

 consists of smaller shells than the type lot, sparsely marked with 

 small stripes and transverse spots of brown or gray in the intervals 

 between the ribs, at least on the upper whorls. Specimens measures 

 Length 31J, diam. 13 mill.; length 34, diam. 12; length 26J, diam. 

 12 mill. There is thus a wide range of variation; and some of the 

 shorter specimens approach C. abacoense, establishing a transition 

 between the tw r o species, which may have to be consolidated. 



C. ALBUM (Maynard). PI. 37, fig. 66. 



Shell with a long and deep umbilical chink, large, solid, cylin- 

 drical and white. Whorls 10^, nearly flat, the latter 3 or 4 of about 

 equal diameter, those above forming a rather straight-sided cone, the 

 apex obtuse; last whorl well rounded beneath. Sculpture of close, 

 regular, rather strong riblets, about as wide as the intervals, and ex- 

 tending to the jftrst whorl, which is smooth ; the riblets becoming 



