114 BULLETIN (18, UNITED STATES NATIONAL MUSEUM. 



spaces. In addition to the axial sculpture the whorls are crossed by 

 twelve deeply incised, somewhat irregularly spaced spiral lines, the 

 raised spaces between which are again divided by many fine striae. 

 All the spiral markings pass over the intercostal spaces and the ribs. 

 Periphery of the last whorl obscurely angular, marked by the feeble 

 continuations of the ribs which yanish immediately below the periph- 

 ery and the usual fine lines of growth and spiral striation. Base 

 rather short, well rounded, brown, with a narrow whitish band about 

 the umbilicus, marked by closely spaced continuous wavy spiral stria- 

 tion, which varies in strength, several finer striaB alternating with the 

 stronger. Aperture subquadrate, outer lip thin, showing four narrow 

 dark-brown bands within, upon a lighter background — these are the 

 three already referred to — and a fourth one on the base adjoining the 

 periphery; columella almost vertical, slightly twisted and revolute. 



The type (Cat. no. 196241, U.S.N.M.) was collected by Rev. G. W. 

 Taylor, atCarter Bay, British Columbia; it has 11 post-nuclear whorls 

 (the nucleus and probably three of the post-nuclear whorls being lost), 

 and measures: Length 13.3 mm., diameter 4 mm. Another specimen 

 from the same locality is in the Taylor collection. Three additional 

 lots were collected by him in British Columbia; 1, a fragment, from 

 west of Rose Spit, Queen Charlotte Islands; 6 at Departure Bay, 1 

 of which is Cat. no. 196242, U.S.N.M.; 15 at Port Sunpson, 5 of 

 which are Cat. no. 196243, U.S.N.M. No. 196242 is the largest 

 specimen, it has 12 J whorls, having lost the nucleus and probably the 

 first three of the succeeding turns, and measures: Length 17.8 mm., 

 diameter 4.5 mm. 



TURBONILLA (MORMULA) TRIDENTATA Carpenter. 



Plate 11, figs. 12, 12a. 



Chemnitzia tridentata Carpenter, Jour, de Conch., vol. 13 (3d ser., vol. 5), 1865, 

 p. 147. Turhonilla (Lancea) tridentata Dall and Bartsch, Mem. Cal. Acad., 

 vol.3, p. 273, 1903, pi. 2, figs. 1, la. Turhonilla ( Mormula) tridentata Dall 

 and Bartsch, Proc. U. S. Nat. Mus., vol. 33, 1907, pp. 511, 512, pi. 45, fig. 9. 



Shell large, broad; chestnut colored, obscurely banded. Nuclear 

 whorls three, helicoid, about one-third immersed, scarcely extending 

 beyond the margin of the spire, their axis being at a right angle to the 

 axis of the later whorls. Post-nuclear whorls slightly convex, some- 

 what contracted at the periphery and slightly shouldered at the sum- 

 mit; traversed by about 20 to 24 strong, well-rounded, somewhat 

 oblique axial ribs, which continue faintly over the decidedly angular 

 periphery of the last whorl and the base to the umbilical region; these 

 ribs are considerably enfeebled on the last whorl of old shells and fre- 

 quently become almost obsolete on these. The exposed portion of the 



