Pvn H,i I'UitlS

12 TEREBRATULID.E.
complete at the lower end : deltidium (or triangular space below
the beak) slight, and divided by the point of the lower
valve: lunge-plate of both valves exceedingly thick, forming
strong supports for the teeth and lamellar processes ; from
these processes extend into the interior two diverging ridges
or septa in the upper valve, and three or more in the lower
valve : teeth of upper valve very strong and projecting towards
each other : sockets in lower valve deep : skeleton consisting
of two thin and elastic blades, which reach within about one-
fourth of the front margin ; they are furnished with upright
spurs at a short distance from the hinge-plate, and have sharp
points. L. 1. B. 0-8.
Yar. oblonga.
Shell much narrower and deeper than usual,
and having the front margin nearly straight.
Habitat :
Rocky and stony ground, from 50 to 90
fathoms, on the north and east coasts of Shetland, but
exceedingly rare in a living state. More than fifty years
ago, when the late Professor Fleming was Minister of
Bressav Island, a stone was brousrht to him by one of
his parishioners, a long-line fisherman, to which three
specimens
of this curious shell were attached. One of
them was sent to Col. Montagu, who described it in the
eleventh volume of the f
Linnean Transactions/ My
late friend Mr. Barlee, as well as myself with Mr. Wal-
ler and Mr. Norman, have lately dredged specimens of
various sizes and ages in the same part of our seas, at
distances from land ranging from one to thirty-five miles.
The locality ("Dublin Bay"), recorded by Dr. Turton
in his (
Conchological Dictionary/ appears to be more
than questionable, especially as he omitted it in his sub-
sequent work on the British bivalves. This species
does not appear to have been found in any of our upper
tertiaries ; but, in all probability, the T. euthyra of Phi-
lippi, a fossil from a corresponding formation in Sicily,
is the same species. T. cranium is rather common on
the Scandinavian coasts; and Dr. Wallich obtained dead