MUSEUM OF COMPARATIVE ZOOLOGY. 203 
Pleurotoma (Drillia) amblytera, sp. nov. 
Plate I. Figs. 5, 5a. 
Three living specimens and one dead, Station 313, off Charleston, S. C., in 
75 fathoms. ¢ 
Two living specimens were dredged by the U. S. Fish Commission in 1883, 
off Cape Hatteras, N. C., in 142 fathoms. 
This species is closely related to the preceding, but has a stouter form, shorter 
and more rapidly tapered spire, ornamented with more conspicuous transverse 
ribs, with a narrower and less perceptible subsutural band, and a larger, more 
prominent apical whorl. 
It also bears a superficial resemblance to Drillia epynota, Dall (this Bulletin, 
XVIII. p. 96, pl. 36, fig. 10, 1889), but the fewer number of its whorls (the 
latter is described as having ten, yet the figure given shows only seven) and 
transverse ribs, with its more strongly marked striz and conspicuous posterior 
sinus, will readily distinguish it. 
_ The animal is drawn so far into the shell in all the specimens as to render 
the study of it impossible. 
Shell consisting of eight whorls, rather thick, of a light yellow color, some- 
times banded with reddish brown. The posterior sinus is nearly round, sit- 
uated just below the suture, and has, in the best developed specimen, a thin, 
sharp edge rising a little above the surface of the shell, bending decidedly 
backward, then curving and nearly meeting in front. The outer lip rounds 
gradually to near the anterior end of the aperture, where it is slightly con- 
tracted, making a short, broad canal, then twisting abruptly backward pro- 
duces a decided notch before joining the columella. A conspicuous varix is 
formed by the thickening of the last rib, beyond which the outer lip is thin, 
white, and sharp-edged. There is a prominent, tooth-like projection on the 
interior of the aperture, at the end of the varix, more conspicuous in some 
specimens than in others, and seen best in an end view. Interior of the 
aperture and inner lip white. Columella straight, with a conspicuous layer 
of enamel having a thin, free edge. Suture distinct, undulating. Subsutural 
band very narrow, concave, lapping well on the preceding whorl. Prominent, 
strong, oblique, rounded ribs, nine on the body whorl, separated by concave 
spaces of about the same width, cross the whorls from suture to suture, faint] Vv 
defined on the subsutural band, and most prominent just below it. On the 
body whorl, these gradually fade away at the base of the siphon, and appear 
on the canal as conspicuous, much curved lines of growth. Microscopic strie 
intersect the fine lines of growth, giving to the entire surface of the shell 
a peculiar crinkled appearance. Nucleus broad, blunt, smooth, somewhat 
shining, consisting of two and a half turns ; the apical whorl large, rising very . 
little above the succeeding one. 
Length of the largest specimen, 15 mm.; greatest breadth, 6 mm.; length 
of aperture, 6 mm. 
