DALL: MOLLUSCA AND BRACHIOPODA. 27 
Ou 
MANGILIINAE. 
BORSONIDA Betrarpi, 1838. 
Borsonia (Borsonella) dalli Arnoxp. 
Plate 13, figure 9. 
Pleurotoma (Borsonia) dalli Arnold, Mem. Cal. Acad. Sci., 1903, 3, p. 201, pl. 6, 
fig. 2. 
Pliocene and Pleistocene of San Pedro, Arnold. U.S. S. ‘“ Albatross,” station 
9839, in 414 fathoms, sand, bottom temperature 41°.4 F., and 2918, in 67 
fathoms, sand, temperature 52°.4; off the edge of the Cortez Bank, N. Pacific 
Ocean. U.S. N. Mus. 96,841 and 122,576. 
Borsonia (Borsonella) agassizii Datt, n. sp. 
Plate 1, figure 5. 
Shell biconic, the aperture shorter than the spire, apex eroded but with six 
remaining whorls, white and chalky under a pale greenish yellow periostracum ; 
suture distinct, not appressed, the whorls sloping flatly to the periphery which is 
marked by a rounded keel with (on the last whorl fifteen) obscure elongated swell- 
ings or nodulations; the anal fasciole which is close to the suture is marked by 
lines of growth concavely arcuate, crossed by half a dozen spiral incised lines in 
the path of the sulcus; below the keel are lines of growth, obscure traces 
of spiral distant incised lines, and numerous irregularly impressed striae, which 
are perhaps pathological ; base moderately convex ; outer lip thin, sharp, strongly 
protractive below the keel, above the latter with a wide, shallow anal sulcus reach- 
ing close to the suture; body polished, milkwhite ; pillar short, twisted, white, « 
with a well-marked spiral plait near its insertion; canal wide, short, distally 
funicular, somewhat recurved. Lon. of shell (decollate), 23; of last whorl, 15 ; 
of aperture, 11; max. diam. 11 mm. 
U.S. S. “ Albatross,” station 3361, Gulf of Panama, in 1471 fathoms, ooze, 
bottom temperature 36°.6 F. U.S. N. Mus. 123,107. 
This species resembles B. diegensis Dall in outline, but is larger, has the carina 
proportionately nearer the middle of the whorl, and the nodulation of the keel is 
strongest on the last whorl; while in diegensis it is more marked on the earlier 
whorls and is sometimes entirely obsolete on the later ones. The latter species 
also has the vermicular impressed sculpture finer and much closer, though this 
may be pathological. 
Borsonia (Borsonella) diegensis Datt, n. sp. 
Plate 13, figure 11. 
Shell small, stoat solid, decollate, with a whitish substratum and strong oliva- 
ceous periostracum ; the four remaining whorls are closely coiled and have the 
