CLASS GASTROPODA 
29 
the next is a little distance posterior to it. Aperture subquadrate; quite 
strongly channeled anteriorly; the junction of the outer and basal lip 
forming almost a right angle; posterior angle obtuse; outer lip very thin, 
showing the external sculpture within and rendered sinuous by the external 
sculpture at the edge; inner lip decidedly oblique, slightly curved, slender, 
reflected and appressed to the base; parietal wall covered by a thin callus. 
Length, 11; diameter, 3.8 mm. (Bartsch.) 
Type in United States National Museum, No. 168753. Type locality, 
off San Juan Island. 
Range. Puget Sound, Washington. 
Bittium serra Bartsch, 1917 
Plate 74, fig. 1 
Proceedings of the United States National Museum , 52:675; PI. 47, fig. 1. 
Shell stout, broadly conic, grayish white. Nuclear whorls decollated. 
Post-nuclear whorls appressed at the summit, strongly rounded, marked by 
slender, rounded, somewhat retractive axial ribs, of which 18 occur upon 
the first and second, 20 upon the third, 22 upon the fourth, and 24 upon 
the remaining turns. In addition to the axial sculpture, the whorls are 
marked by four spiral cords, of which the first, which is at the summit, 
is a little weaker than the rest. The junctions of these cords with the axial 
ribs form prominent, strongly rounded tubercles, while the spaces inclosed 
between them are rounded pits. Suture moderately constricted but not 
channeled. Periphery of the last whorl rendered angulated by a spiral 
cord. Base short, slightly concave, marked by four, very low, broad, 
almost equal, spiral cords, which are separated by mere impressed lines. 
Aperture oval, narrowly twistedly channeled anteriorly; posterior angle 
obtuse; outer lip rendered wavy by the external sculpture; inner lip 
decidedly curved, somewhat revolute, reflected over and appressed to the 
base; parietal wall covered with a thin callus. Length, 6.5; diameter, 2.6 
mm. (Bartsch.) 
Type in United States National Museum, No. 271076. lype locality, 
U.S. Bureau of Fisheries Steamer “Albatross,” Station 4310, off Point 
Loma Light, California, in 71-75 fathoms. 
Range. Off Point Pinos to San Diego, California, and San Bertolome 
Bay, Lower California. 
Bittium tumidum Bartsch, 1907 
Proceedings of the United States National Museum, 33:179. 
Shell of medium size, light yellowish-brown, shining. Nuclear whorls 
decollated. Post-nuclear whorls somewhat inflated, well-rounded, sepa- 
[6311 
