34 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Bittium munitum munitoide Bartsch, 1911 
Proceedings of the United States National Museum, 40:405; PI. 53, fig. 4. 
This is the southern race of Bittium munitum. It differs from B. muni¬ 
tum proper in being smaller and in having many more ribs, as many as 40 
occurring upon the last whorl. Length, 8.2; diameter, 2.8 mm. (Bartsch.) 
Type in United States National Museum, No. 152164. Type locality, 
San Pedro, California. 
Range. Known only from type locality. 
Bittium asperum lomaense Bartsch, 1911 
Proceedings of the United States National Museum, 40:406; PI. 56, fig. 2. 
Shell similar to B. asperum Gabb, but differing in being uniformly 
smaller, more slender, and in having more ribs. A specimen of B. asperum 
with 10 post-nuclear whorls measures: Length, 8.1 mm.; while one of 
B. a. lomaense of the same number of whorls measures 7.1 mm. B . a. 
lomaense is a living representative of B. asperum , which is a Post-Pliocene 
species. Length, 7.1; diameter, 2.3 mm. (Bartsch.) 
Type in United States National Museum, No. 195130. Type locality, 
U. S. Bureau of Fisheries Station 4310, in 71-75 fathoms, off Point Loma 
Light, California. 
Range. Catalina Island to San Diego, California. 
Bittium larum Bartsch, 1911 
Plate 77, fig. 4 
Proceedings of the United States National Museum , 40:407; PI. 57, fig. 4. 
Shell very regularly elongate-conic, light brown. Nuclear whorls at 
least two, worn. Post-nuclear whorls appressed at the summit, decidedly 
overhanging. The early post-nuclear whorls are marked by four equal and 
equally spaced spiral cords, the first of which is at the summit; these cords 
divide the space between the sutures into four equal parts. On the sixth 
whorl intercalated spiral cords make their appearance in the middle, be¬ 
tween all the primary cords; these attain a little more than half the strength 
of the primary cords on the last turn. In addition to the spiral sculpture, 
the whorls are marked by moderately strong, almost vertical, axial ribs, of 
which 14 occur upon all but the penultimate turn, which has 18. The 
intersections of the axial ribs and spiral cords form elongate tubercles, 
which have their long axes parallel with the spiral sculpture. The spaces 
inclosed between the axial ribs and the spiral cords are rectangular pits 
on the early whorls, and broad, incised lines on the later ones. Sutures 
[636 ] 
