Pvn H,i I'UitlS

NUCULA. 151
B. Inner margin plain.
4. N. te'nuis*, Montagu.
Area tenuis, Mont, Test. Brit. Suppl. p. 56, tab. 29. f. 1. N. tenuis, F. & H.
ii. p. 223, pi. xlvii. f. 6, and (animal) pi. P. f. 5.
Body white : mantle open in front and at the posterior side,
with a : plain edge foot white, rather longer and not so decidedly
pedunculated as in the other species, nor are the margins of its
disk so coarsely serrated, although the crenulations are more
numerous.
Shell obtusely and obliquely triangular, and inclining to a
circular form, compressed, thin, glossy : sculpture, only slight
and irregular transverse ridges : colour bluish-white under the
epidermis, which is yellowish, with a tinge of light brown,
highly polished and lustrous, and destitute of microscopical
or any other markings : margins truncate at the anterior side,
and obtusely angled at the point of junction with the ventral
range, rounded and broad in front, and slightly produced or
wedge-shaped on the posterior side : beaJcs blunt, and scarcely
prominent, not much recurved: lunule comparatively small
but raised, denned by a :
slight ridge ; ligament strong carti-
lage pear-shaped, contained in a rather large and broad cavity :
hinge-line curved, occupying about one-third of the circumference
of the shell: hinge-plate forming an oblique groove
on each side of the beak : teeth long, sharp, and nearly straight,
about six on the anterior, and sixteen on the posterior side :
inside silvery-white and iridescent, faintly striated lengthwise,
with the margin somewhat thickened : muscular scars
roundish-oval, rather distinct. L. 0-425. B. 0-45.
Var. inflata.
with the front or ventral margin
Shell smaller, more triangular and tumid,
less curved :
beetles
more pro-
minent. L. 0-3. B. 0-3. N. inflata, Hancock, in Ann. & Mag.
Nat. Hist, xviii. p. 333, pi. v. f. 13, 14.
Habitat : Sand and mud, in 25-100 fathoms, on the
north-east coast of England, every part of Scotland
from the Firth of Forth to Unst, Dublin Bay, and
(according to the late Mr. Thompson)
the east of Ire-
land. It is, however, a local species. Dr. Goodall was
* Thin.