DALL: MOLLUSCA AND BRACHIOPODA. 281 
Pleurotomella (Pleurotomella) polystephanus Da tt, n. sp. 
Shell of moderate size of six or more whorls, the apex eroded, white, with a 
cream-colored periostracum ; spiral sculpture of numerous fine, subequal, flattish 
threads with narrower interspaces, which cover the whole shell; to these are added 
a thickened ridge which borders the anterior margin of the suture, and on the spire 
, a peripheral nodose keel, which is less marked on the last whorl, where it forms 
the shoulder; on the penultimate whorl there are twenty of these nodules; other 
axial sculpture is furnished by fine, short, sharp elevated wrinkles which cross 
retractively the ridge adjacent to the suture, like the “gathers” of a skirt, and 
become obsolete on the fasciole ; there are twenty-eight of these wrinkles on the 
margin of the penultimate whorl; the space above the shoulder is distinctly 
excavated, especially on the spire; suture distinct and, on the earlier whorls, 
almost channelled; aperture ovate ; anal fasciole comprised in the nodose shoulder, 
not reaching the suture; outer liparcuately produced forward; pillar with a thin, 
smooth layer of enamel, obliquely attenuated distally, somewhat twisted; canal 
wide, shallow. Lon. of shell, 25; of last whorl, 19; of aperture, 14.5; max. 
diam. 12.5 mm. 
U. 8. S. “ Albatross,” station 2808, near the Galapagos Islands, in 634 
fathoms, sand, bottom temperature 40° F. U.S. N. Mus. 96,498. 
The several encircling rows of nodosities or wrinkles give this shell a particu- 
larly elegant appearance. 
Pleurotomella (Pleurotomella) dinora Datz1, n. sp. 
Shell small, short-fusiform, stout, white with a pale yellowish periostracum, and 
about seven whorls; apex defective, subsequent whorls rather rapidly increasing, 
with an appressed suture behind a smooth and constricted anal fasciole in front of 
which the shell is shouldered by a series of short, slightly protractive ribs, of 
which, on the penultimate whorl there are fifteen, with subequal interspaces and 
crossed by half a dozen irregularly spaced spiral striations ; these striae are ill 
defined, and on the last whorl extend over the base of the shell to the canal; on 
the last half of the last whorl the ribs become obsolete; aperture narrow, anal 
sulcus at the suture wide and deep, the outer lip in front of it prominently arcu- 
ate, thin and simple; pillar lip smooth with a thin wash of callus ; pillar twisted, 
rapidly attenuated; axis impervious; canal moderately wide, short and slightly re- 
curved. Length of (decollate) five whorls, 15; of last whorl, 11; of aperture, 8 ; 
max. diam. 7 mm. 
U.S. 5S. ‘ Albatross,” station 2807, near the Galapagos Islands, in 812 fathoms, 
ooze, bottom temperature 38°.4 F. U.S. N. Mus. 96,479. 
This a pretty but small form, which recalls in its general aspect several of the 
larger Atlantic species. 
