no. 1826. MOLLUSES OF THE GENUS BITTIUM— BARTSCH. 391 



BITTIUM (SEMIBITTIUM) ARMILLATUM Carpenter. 



Plate 52, fig. 6. 



Bittium ar-millatum Carpenter, Rep. Brit. Ass. Adv. Sci. for 1863, 1864, p. 655. 

 Bittium armillatum Carpenter, Ann. Mag. Nat. Hist., ser. 3, vol 18, 1866, p. 276. 



Shell broadly conic, rust brown. Nuclear whorls at least 3, ap- 

 parently smooth. Post-nuclear whorls shouldered at the summit, 

 marked by three strong spiral keels which are considerably narrower 

 than the three spaces into which they divide the whorls between the 

 sutures. In addition to the spiral sculpture the whorls are marked 

 by slightly retractive axial ribs, which are about as strong as the spiral 

 keels. Of these, 16 occur upon the fourth, 18 upon the fifth, 20 upon 

 the sixth, 24 upon the seventh, and 32 upon the penultimate turn. 

 The junctions of the axial ribs and the spiral cords form well-rounded 

 tubercles, while the spaces inclosed between are well-impressed 

 squarish pits. Sutures strongly constricted. Base moderately long, 

 ornamented by six low, well-rounded, subequally spaced spiral cords. 

 Aperture channeled anteriorly ; posterior angle obtuse ; outer lip ren- 

 dered sinuous by the external sculpture; columella moderately long, 

 oblique, curved, and reflected ; parietal wall covered with a moderately 

 thick callus. 



The type (Cat. No. 15653, U.S.N.M.) comes from the Lower Pleisto- 

 cene deposits of Santa Barbara, California. It has nine post-nuclear 

 whorls and measures: Length 9.5 mm., diameter 3.2 mm. Another 

 specimen, also fossil (Cat. No. 195160, U.S.N.M.), comes from San 

 Pedro, California. 



BITTIUM (SEMIBITTIUM) PURPUREUM Carpenter. 

 Plate 52, figs. 1 and 3. 



Cerithiopsis purpurea Carpenter, Rep. Brit. Ass. Adv. Sci. for 1863, 1864, p. 660. 

 Cerithiopsis purpurea Carpenter, Ann. Mag. Nat. Hist., ser. 3, vol. 15, 1865, 

 p. 337. 



Shell broadly elongate conic, wax-yellow, variously mottled and 

 banded with chestnut brown. Nuclear whorls a little more than one, 

 apparently smooth. Post-nuclear whorls marked by three strong 

 spiral cords, which divide the space between the suture and the sum- 

 mit into three almost equal areas. The cord at the summit is very 

 slightly below the summit and renders this strongly shouldered. 

 In addition to the spiral sculpture, the whorls are marked by almost 

 vertical, axial ribs which are nearly equal to the spiral cords in 

 strength. Of these, 14 occur upon the first, 16 upon the second, 18 

 upon the third, 20 upon the fourth, 22 upon the fifth, and 25 upon the 

 penultimate turn. The intersections of the spiral cords and the axial 

 ribs form well-rounded tubercles, while the spaces inclosed between 

 them are well-impressed squarish pits on all but the last; on this 

 they are oblong, their long axes coinciding with the axial sculpture. 

 Sutures strongly constricted, showing the peripheral cord on the later 



