Pvn H,i I'UitlS

206 KELLIIDJE.
lines of growth : colour yellowish -white : epidermis extremely
thin : margins abruptly
truncate but rounded at the smaller or
posterior end, with an oblique slope to the ventral margin,
which is also curved and rather deeply indented for the
and rounded at the anterioi
byssus, very broad, wedge-shaped,
end, and forming an obtuse angle
behind :
beaks
small, blunt,
and nearly straight, protruded beyond the dorsal margin ; they
are placed very much nearer to the posterior side, which is
not one-fourth the size of the other : hinge-line slightly curved,
occupying about one-fifth of the circumference : cartilage
yellowish-brown and semicylindrical, clasping the hinge-line
short and
on the posterior side of the beaks : hinge-plate
narrow, but strong, not deeply excavated in the middle :
triangular and pointed,
teeth
that on the anterior side in each valve
the teeth in one
being longer and rather larger than the other ;
valve lock into sockets in the other, but not in the corresponding
valve of every specimen — it apparently being indifferent
whether the right or left valve contains the more prominent
teeth or the sockets : inside nacreous and glossy, with a plain
margin :
pallial and muscular scars indistinct, the former being
more perceptible than the latter. L. 0*115. B. 0*125.
Var. Icevis. Shell smooth and destitute of the radiating
striae.
Habitat : On
the ventral spines of Spatangus pur-
pureus, and occasionally of Amphidetus ovatus (A. roseus,
Forbes), in sandy ground, at depths ranging from 8 to
90 fathoms, on every part of our coasts. Capt. Beechey
took it alive on the Spatanyus in 110-140 fathoms off
the Mull of Galloway. The variety is from deep Avater
in Shetland. It is a Coralline Crag species. Loven,
Sars, Asbjornsen, M'Andrew, and Malm have recorded
it as inhabiting the Scandinavian seas from Finmark
southwards, Petit as found in the north of France, and
Recluz, Verany, and Mace as Mediterranean. The last-
named conchologist informs me that it occurs in the
Gulf of Lyons on Cidaris hy stria;. Sars mentions that
at Naples it attaches itself to Spatangus meridionalis ;
and Malm says that on the coast of Bohuslan not only
S. purpureus and A. ovatus, but also Brissits lyrifer, are