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312 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
shell) pale brownish yellow; the spire, when worn, and the interior, yel- 
lowish brown. Other specimens are white or yellowish white. Length, 
2m. breadth, 25"; length of aperture, 27™"; its breadth, 15™”. 
This shell was first dredged by me near Eastport, Me., in 1870. It 
has since been dredged by the United States Fish Commission parties 
in Casco Bay, Me., and also off Block Island, stations 812 to 814, in 26 to 
28 fathoms. It is still a very rare species. It has some resemblance to 
Acrybia flava, on account of the lightness and thinness of the shell, as 
well as in form, but the shape of the aperture is different, and there is 
a distinct umbilicus. The columella is also much less ineurved. 
Lamellaria pellucida Verrill. 
Amer. Journ. Sci., xx, p. 395, for Nov. (published Oct. 25, 1880). 
Animal broad-elliptical, well rounded, both anteriorly and posteriorly ; 
back convex or somewhat swollen, smooth, without tubercles ; branchial 
sinus, in anterior edge of mantle, shallow but distinct; tentacles slen- 
der, tapered; eyes small, black, on the outer basal portion of the tenta- 
cles; foot oblong, well developed, reaching nearly to the posterior end 
of the mantle when extended. Color of the mantle yellowish brown, 
blotched irregularly with dark brown; some specimens were paler, 
others darker brown. 
Odontophore long and narrow, with three rows of teeth; central 
tooth much smaller than the lateral, its basal part oblong, with nearly 
parallel sides and squarely truncate at the end; tip acute-triangular, 
strongly curved forward, with a prominent, sharp, median denticle, and 
a row of four or five much smaller denticles on each side. Lateral teeth 
very large, strongly incurved, and hollowed out on the concave surface, 
with both edges serrate; the inner edge has the serrations coarser, not 
reaching the tip, which is smooth, stout, acute. The basal portion of 
the lateral teeth is furnished with a broad, sinuous, aliform lobe on the 
outer edge; the basal end is slightly expanded and obtusely round or 
subtruncate. 
The most important difference between the dentition of this species 
and that of DL. perspicua and L. latens (Miill.) is in the form of the basal 
portion of the median teeth; in both the European species this is 
divided into two divergent lobes, separated by a deep notch. 
Shell ovate, with a well-formed spire, very thin and delicate, smooth, 
lustrous, and transparent. Aperture broad-ovate, much larger than the 
body of the shell, but not so large and open as in ZL. latens. The in- 
terior of the spire cannot be seen in a ventral view, but is visible in an 
end view from the front. The spire is oblique, somewhat elevated, and 
slightly pointed, with a minute nucleus. Whorls three, well rounded; 
sutures impressed. Outer lip very thin, sloping or somewhat flattened 
posteriorly, somewhat expanded and well rounded anteriorly ; inner lip 
receding in a deep, regular incurvature of the body-whorl, which has ¢ 
sharp, thin edge that winds spirally into the interior of the spire. Sculp- 
