250 



CEKION, GROUP XI. 



C. RITCHIEI (Maynard). PI. 39, figs. 91 , 92. 



Shell large, rimate, cylindric, solid and strong; impure white with 

 white ribs and brown or gray stains in many of the interstices, or all 

 of the intervals may be purplish-brown. Sculpture of even, strong, 

 nearly straight ribs, usually a little narrower than their intervals, 25 

 to 28 in number on the penultimate whorl. Whorls about 11|, 

 slightly convex. Aperture small, brown or dark gray within ; peri- 

 stome white, very narrowly expanded, the margins connected by a 

 strony, straight, raised ledge across the parietal wall. Parietal lamella 

 very stout, blunt and heavy, rather short. Axial lamella small. 



Length 35, diam. 13^, longest axis of aperture 12 mill. 



Length 37, diam. 14, longest axis of aperture 12 mill. 



Length 341, diam. 14 mill. (type). 



Bahamas : Highborn Key, the typical form found about the head 

 of the bay on the south side, along the eastern hills northward for 

 about a mile, and southward to the southern point of that portion of 

 the key ; westward it spreads to the front of the hills of that division 

 of the key, but is not found on them (Maynard). 



Strophia ritchiei MAYN., Contrib. to Sci. ii, p. 135, fig. 41. Stro- 



phia grayi MAYN., t. c., p. 138, f. 42, 43. 8. grayi gigantea MAYN., 

 t. c., p. 141, f. 44o S. grayi pumilia MAYN., t. c., p. 143, f. 44b 

 (Dec., 1894) Cerion ritchiei vannostrandi P. & V., Proc. A. N. S., 

 Phila., 1896, p. 323, no. 35d. 



This species is distinguished by its large size, the very slightly 

 expanded or unexpanded lip, prominent parietal callus and stout 

 parietal toolh. Mr. Maynard describes several forms, which are, 

 however, only selected specimens. Form no. 1, with the size and 

 shape of the type, has about 25 ribs on the last whorl; the type shell 

 having 23. The color is darker within and between the ribs (pi. 39, 

 fig. 92). Form no. 2 is smaller, 27^xll| mill., with 10 whorls and 

 16 ribs on the last. Form no. 3 is cylindric, with 11 whorls, with 

 fewer ribs, the number sometimes as low as 18 on the last whorl. It 

 forms a transition to grayi. Form no. 4 has the contour of the type, 

 but the aperture is wider, more open, and the ribs more numerous, 

 34 on the last whorl. There are numerous intermediate examples. 



Form grayi (Maynard). PI. 39, figs. 93, 94, 98, 99. 



Usually perforate, white, uniform or stained with blue at the base 

 and in some of the intercostal spaces, cylindric, solid and strong. 



