MARINE MOLLUSCA OF THE UNITED STATES. 51 
Genus PLEUROTOMELLA, Verrill. 
Am. Journ. Science, v. 15. 1873. 
1. P. Packarptl, Verrill. 
Am. Journ. Science, y. 15. 1878. 
Shell thin, fragile, translucent, pale flesh-colored, moderately 
stout, with an acute, somewhat turreted spire; whorls nine, the 
apical whorls, for about two and a half turns, nearly smooth, regu- 
lar, convex, chestnut-colored; below this the whorls are shoul. 
dered, strongly convex in the middle, but with a smooth concave 
band below the suture, corresponding to the posterior notch in the 
outer lip; the whorls are crossed below the subsutural band by 
about sixteen strong, prominent, rounded, somewhat oblique ribs, 
most prominent on the middle of the whorl, but not angulated ; 
on the last whorl these ribs become very oblique below the middle, 
and follow the curve of the edge of the lip, nearly fading out an- 
teriorly ; the surface between the ribs is marked by faint lines of 
growth, and by fine, unequal, slightly raised revolving lines, which 
pass over the ribs without interruption. They become more evi- 
dent on the lower part of the last whorl, and are very faint on the 
subsutural band, which is more decidedly marked by receding, 
strongly curved lines of growth. The aperture is rather broad 
above, elongated below, sub-oval, outer lip very thin, sharp, pro- 
minent above, separated from the preceding whorl by a wide and 
very deep sinus, extending back for about one-fifth of the circum- 
ference of the whorl; the anterior border of the lip is incurved 
near the end and obliquely truncate, forming a short, straight 
canal. Columella simple, nearly straight, its inner edge towards 
the end sharp and obliquely excurved. 
Length 22, diam. 12 mill. 
Bay of Fundy, ete. 
Genus MANGELIA, Risso. 
Moll. Eur. Merid. f. 101. 1826. 
1. M. RUBELLA, Kurtz and Stimpson. 
Proc. Bost. Soc. Nat. Hist., iv. 115. 1851. 
Shell ovately fusiform, longitudinally costate, ribs elevated, 
acute, spirally finely striate; whorls seven, angulate, the last 
three-fourths the length of the shell; aperture narrow, one-half the 
total length, lip thickened, scarcely sinuate; ribs wax-colored, 
