Pvn H,i I'UitlS

PSAMMOBIA. 393
golden yellow, but afterwards horncolour, more or less annu-
lated, separating the valves (as in T. donacina) by an ellip-
tical gape : corselet short but deep : hinge-line almost straight
or very little curved in the adult, obtusely angular
in the
young, occasionally stained inside with rose-colour : hinge-
plate narrow and thick, abruptly
truncate at the outer end of
the ligament : teeth, in the right valve two small knob- like
and diverging cardinals, the anterior being a trifle the larger ;
in the left valve a small erect cardinal in the centre of the
hinge, seated in a cavity,
besides another minute laminar
one in a line with the beak and at a right angle to the edge
of the hinge-plate ; the three largest teeth are bifid : inside
polished and very glossy, coloured and rayed like the outside,
and sometimes having a short white longitudinal streak
below the beak, microscopically fretted indistinctly
throughout, and
striated lengthwise towards the edge, which is
thickened: pdtlial scar well defined ; sinus oval, not very large
or deep, extending from the posterior muscular scar about
halfway across the interior, apparently double in consequence
of a shifting or enlargement of the tubular base : muscular
scars irregularly triangular, anterior the larger of the two.
L. 0-6. B. 1-15.
Var. gracilis. Shell broader in proportion to its length,
flatter, and of a slighter consistency, somewhat gaping at both
ends ; a few of the concentric striae assuming the form of
irregular grooves or ridges ; colouring more delicate, sometimes
bright orange or marked with short purplish streaks,
and not unfrequently milk-white with dusky or pure white
streaks.
Habitat : English, Welsh, Irish, and Scotch coasts,
from one extremity to the other, in sand and among
nullipores, at depths betAveen 4 and 85 fathoms, but
locally distributed. The variety is from deep
water off
Shetland, and resembles Galeomma Turtoni in shape.
P. tellinella is a fossil of the Coralline Crag. It inhabits
the upper and western coasts of- Norway, in 3-40 fa-
thoms ; and M'Andrew has taken it on the Lusitanian
coasts,
in 15-30 fathoms.
It is an active little mollusk burrowing and swimming
s 5