276 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
aperture longer than the remaining portion of the spire; the sculpture consists of 
a strong spiral keel, peripheral on the spire with more or less nodulation (in one 
specimen with fifteen small modules on the penultimate whorl, but none on the 
last whorl; another has them obsolete on the spire), stronger on the earlier whorls 
when present, an obscure ridge in front of the suture, stronger on the earlier 
whorls, faint spiral striation on the anal fasciole between the ridge and the keel, 
the whole surface covered with a microscopic, close, impressed, vermicular net- 
work of fine lines anastomosing in every direction; on the last whorl the keel is 
well above the periphery; base evenly rounded, aperture ample, anal sulcus at 
the suture wide and deep; outer lip thin, arcuately produced; pillar lip smooth, 
with a glaze of callus, the plication on the proximal part of the pillar lagging 
behind the aperture; canal very wide and short with an obsolete fasciole. Length 
of four whorls, 15.0; of last whorl, 12.5; of aperture, 9.5; max. diam. 8.0 mm. 
U. S. S. “ Albatross,” station 2923, off San Diego, California, in 822 fathoms, 
mud, bottom temperature 39°F. U.S. N. Mus. 122,573. 
Like the preceding species this has the plication on the pillar hardly visible 
from the aperture. 
Borsonia (Borsonella) hooveri ARrno.p. 
Plate 13, figure 7. 
Pleurotoma (Borsonia) hooveri Arnold, Mem. Cal. Acad. Sci., 1903, 3, p. 201, pl. 10, 
fig. 1. 
Shell small, chalky-white, covered with a polished olive-gray periostracum ; 
apex eroded, leaving indications of about six whorls; general form biconic with 
a single sharp keel at the shoulder, between which and the suture the whorl is 
more or less excavated ; suture distinct, the margin in front of it turgid, giving 
an effect as if minutely channelled ; excavated area forming the anal fasciole, with 
arcuate growth lines, crossed by about six faint incised distant spiral lines; keel | 
somewhat above the periphery, with a rounded and somewhat compressed edge 
without waves or nodulations; surface in front of the keel moderately convex, 
spirally sculptured by obsolete distant lines crossed by fine irregular slightly ele- 
vated incremental lines, which, in spots, produce a vermiculate aspect; base a 
little constricted behind the short, nearly straight, attenuated canal; body with 
a wash of callus; outer lip with a wide, moderately deep, rounded anal sulcus ; in 
front of the keel markedly protractive, thin and simple; pillar straight, moder- 
ately callous, with a single strong almost horizontal plait near its insertion, ante- 
riorly obliquely truncate, twisted, not pervious; canal very short. Lon. of 
(decollate) shell, 14.7; of last whorl, 10; of aperture, 7.5; max. diam. 8 mm. 
Pleistocene of San Pedro, Califormia, Arnold. 
U.S. S. “ Albatross,” station 3431, off Mazatlan, Mex., in 995 fathoms, mud, 
bottom temperature 37° F. U.S. N. Mus. 123,110. Also at station 3392, Gulf of 
Panama, in 1270 fathoms, hard bottom, temperature 36°.4; and station 3576, on 
the coast of Ecuador, in 1132 fathoms, ooze, temperature 36° F. 
