no. 1826. 



MOLLUSKS OF THE GENUS BITTIUM— BARTSCH. 



395 



BITTIUM (SEMIBITTIIJM) ATTENUATUM BORE ALE, new subspecies. 

 Plate 54, fig. 4. 



Shell similar to Bittium attenuatum, but in every way larger and 

 more robust. Sculpture very much stronger than in the typical 

 form; the tubercles well developed on the last whorl, but much weaker 

 than on the earlier ones. 



The type and fourteen specimens (Cat. No. 211586, U.S.N.M.) come 

 from Barclay Sound, 8-27 fathoms, Vancouver Island. The type 

 has eight post-nuclear whorls and measures: Length 10.1 mm., diam- 

 eter 3.5 mm. Eighteen additional specimens from the same localit}^ 

 are in the Dominion Geological Survey. 



BITTIUM (SEMIBITTIUM) ATTENUATUM MULTIFILOSUM Bartsch. 



Plate 54, fig. 3. 

 Bittium esuriens multifilosum Bartsch, Proc. U. S. Nat. Mua., vol. 33, 1907, p. 179. 



Shell similar to B. attenuatum, but having seven spiral keels be- 

 tween the sutures on the whorls of the spire instead of four; that is. a 

 strong, intercalated spiral cord between each of the four primary keels. 



The type (Cat. No. 127051, U.S.N.M.) comes from Whites Point, 

 San Pedro, California. It has ten whorls and measures: Length 9.2 

 mm., diameter 3 mm. 



Specimens examined. 



1 Type. 

 BITTIUM (SEMIBITTIUM) ATTENUATUM LATIFILOSUM, new subspecies. 



Plate 54, fig. 6. 



Shell similar to Bittium attenuatum. Whorls a little higher between 

 the sutures than in the typical form, with four spiral cords between 

 the sutures, which are much broader than in typical attenuatum. 

 The axial ribs are strong on the early whorls, but scarcely indicated 

 on the last volutions. Shell usually mottled. 



The type (Cat. No. 109509, U.S.N.M.) comes from Terminal Island, 

 California. Two additional specimens (Cat. No. 153086, U.S.N.M.) 

 come from San Pedro, California. 



BITTIUM (SEMIBITTIUM) SUBPLANATUM, new species. 



Plate 57, fig. 5. 



Shell broadly elongate-conic, milk white. Nuclear whorls a little 

 more than one, well rounded, smooth. The first of the post-nuclear 

 whorls well rounded, marked by three spiral cords, one of which is at 



