24 MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
cidedly overhanging, the early ones marked by two strong spiral cords on 
the anterior half between the sutures, and a third less strongly developed 
cord at the summit. On the third whorl a fourth spiral makes its appear¬ 
ance between the one at the summit and its neighbor; this fourth spiral 
soon increases in size, so that on the middle of the shell all four cords are 
practically of equal strength and spacing. On the last whorl a slender, 
intercalated cord appears between the anterior two. In addition to the 
spiral sculpture, the whorls are marked by strong, well-rounded, axial ribs, 
which are merely indicated on the first two whorls; on the third to sixth 
turn there are 14, on the seventh there are 16, on the eighth, 18, and on 
the penultimate whorl 24. The intersections of the axial ribs and spiral 
cords form elongated tubercles, which have their long axes parallel with 
the spiral sculpture. The spaces between the spiral cords and axial ribs 
are elongated, squarish pits. Sutures strongly constricted. Periphery of 
the last whorl marked by a channel which bears a slender cord. Base well- 
rounded, marked by six spiral cords, which grow successively weaker and 
more closely spaced from the periphery to the umbilical area. Aperture 
oval, channeled anteriorly; posterior angle acute; outer lip thin, rendered 
sinuous by the external sculpture; columella short, twisted, and reflected. 
Length, 10.5; diameter, 3.5 mm. (Bartsch.) 
Type in United States National Museum, No. 7154. Type locality, 
Lower Pleistocene, Santa Barbara, California. 
Range. San Pedro and Catalina Island, California. Fossil, Lower 
Pleistocene of Santa Barbara, Terminal Island, San Pedro, and San Diego, 
California. 
Bittium quadrifilatum Carpenter, 1864 
Plate 73, fig. 4; Plate 79, figs. 2, 3 
Journal dc Conchyliologie, 13:143. 
B. t. satis tereti, pallide, cinerea, tenuisculpta; anfr. nucleosis, primo 
omnino coelato, sinistrali, dein 2 laevibus, rotundatis, apice quasi mamil- 
lato; anfr. normalibus, subplanatis; suturis valde impressis, haud sculptis; 
costulis radiantibus circ. 15-22, angustis subrcctis, anfr. ult. crebrioribus, 
suturam versus evanidis; filis spiralibus semper aequilibus, supra spiram 4 
sagustis, expressis, costulas transeuntibus, haud nodulosis; filis duabus 
alteris, inter quas sutura sita est; basi tenue striata; columella intorta, 
parum effusa; apertura ovata; libio parvulo labro tenui, parum arcuato. 
Long., 26; long, spir., 16; lat., 9 poll. (Carpenter.) 
Shell rather large, elongate-conic, chestnut brown, dull. Nuclear whorls 
two, well-rounded, smooth, the first obliquely tilted. Post-nuclear whorls 
shouldered at the summit, moderately rounded, ornamented with four 
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