% 

 NO. 2193. WEST AMERICAN MARINE MOLLUSKS—BARTSCH. 673 



constricted, channeled. Periphery of the last whorl rendered angu- 

 lated by a cord, the groove between which and the fourth cord of the 

 spire is crossed by two slender spiral threads. Base short, concave in 

 the middle, marked by seven subequal and subeqiially spaced low 

 rounded spiral cords, which are about as wide as the spaces that 

 separate them, and numerous very fine axial threads which are best 

 shown in the grooves. Aperture oval, slightly protracted and weakly 

 channeled anteriorly ; posterior angle obtuse ; outer lip thin, rendered 

 sinuous hj the external sculpture ; inner lip oblique, slightly curved, 

 reflected over and appressed to the base; parietal wall covered by a 

 thin callus. 



The type. Cat. No. 266937, U.S.N.M., was dredged in shallow 

 water in San Bartolome Bay, Lovv-er California. It has 7^ post- 

 nuclear whorls and measures — length, 6.6 mm. ; diameter, 2.6 mm. 



BITTIUM CHALLISAE, new species. 



Plate 47, figs. 2, 6. 



Shell very large, white. Nucleus and early postnuclear turns de- 

 collated, those remaining slightly shouldered at the summit, weakly 

 rounded in the middle and decidedly contracted immediately above 

 the suture, marked by rather strong, low, well-rounded axial ribs of 

 which 14 occur upon the second and third, 16 upon the fourth to 

 sixth, 18 upon the seventh, and 20 upon the last turn. The spiral 

 sculpture consists of four cords on the early whorls, of which the 

 first, at the summit, is a little weaker than the rest. These primary 

 cords are truncated posteriorly and slope gently anteriorly. Begin- 

 ning with the fourth whorl an intercalated thread makes its appear- 

 ance between all the cords and between the summit and the first cord. 

 Suture strongly constricted. Periphery of the last whorl rendered 

 angulated by a cord. Base short, slightly concave, marked by five 

 low, broad, well rounded, obsolete cords which are subequal and sub- 

 equally spaced. Aperture broadly oval, rather strongly channeled 

 anteriorly; posterior angle obtuse; outer lip thin rendered sinuous 

 at the edge by the external sculpture, showing the external markings 

 within ; inner lip somewhat sinuous, rather stout, reflected over and 

 appressed to the base; parietal wall covered by a moderately thick 

 callus. 



The type and another specimen. Cat. No. 272376, U.S.N.M., were 

 collected by Miss Bertha Challis at San Juan Island, Gulf of Greor- 

 gia, British Columbia. The type has nine whorls remaining and 

 measures — length, 13 mm. ; diameter, i.2 m.m. 

 6500S°— Proe.N.M.vol..52— 17 43 



