no. 1826. 



MOLLU8K8 OF THE GENUS BITTIUM—BARTSCII. 



403 



The type (Cat. No. 165232, U.S.N.M.) comes from the Pleistocene 

 at Santa Barbara, California. It has nine and one-half post-nuclear 

 whorls, and measures: Length 7.5 mm., diameter 2.8 mm. The 

 present species occurs both recent and fossil. The recent shells are 

 slightly slenderer than the fossil form. 



Specimens examined. 



1 Type. 



BITTIUM (LIROBITTIUM1 CATALINENSE INORNATUM, new subspecies. 



Plate 51, fig. 3. 



Shell similar to Bittium catalinense, but lacking the plain spiral keel 

 in the suture. 



The type (Cat. No. 195153, U.S.N.M.) comes from 40 fathoms off 

 Catalina Island, California. It has ten post-nuclear whorls, and 

 measures: Length 7.2 mm., diameter 2.3 mm. Another specimen 

 (Cat. No. 193695, U.S.N.M.) is also from Catalina Island, while a 

 third (Cat. No. 148649, U.S.N.M.) comes from the Lower Pleistocene 

 deposits at San Diego, California. 



BITTIUM (LIROBITTIUM) ORNATISSIMUM, new species. 



Plate 52, figs. 4 and 5. 



Shell elongate-conic, creamy white. Nuclear whorls one and one- 

 half, marked by two slender threads which divide the space between 

 the sutures into three equal parts. Post-nuclear whorls strongly 

 shouldered at the summit, marked by three strong spiral keels which 

 divide the space between the sutures into four almost equal parts. 

 The space between the first of these keels below the summit and the 

 summit is a little narrower than the rest. In addition to these three 

 strong spiral keels, intercalated keels are present, the first of which 

 is at the summit, while another occurs between each of the other 

 keels. On the last whorl these attain a strength almost equal to that 

 of the primary keels. In addition to this spiral sculpture, the whorls 

 are marked by well-developed, slightly retractive, axial ribs, of which 

 14 occur upon the first and second, 15 upon the third, 16 upon the 

 fourth, 18 upon the fifth and sixth, 20 upon the seventh, 22 upon the 

 eighth, 28 upon the ninth and tenth, and 34 upon the penultimate 

 turn. The intersections of the axial ribs and spiral keels form strong 



