Pvn H,i I'UitlS

374 TELLINID.E.
and contiguous umbones ; projecting, but not disproportionately
convex : lunule deep, lanceolate, elongated, and of a reddish-brown
hue : ligament long, rather prominent, dark horncolour
: hinge-line curved : hinge-plate thick, broad, and flexu-
ous : teeth similar to those in T. balaustina, but stronger ; the
anterior lateral in the right valve is very large and conspicuous
: inside highly glossy and nacreous, longitudinally marked
towards the margin with faint and indistinct lines, and sometimes
streaked irregularly from the hinge to the centre with
bright pink or rosecolour : pallial scar well defined, large, extending
across nearly to the anterior adductor muscle, and
slightly lineated in the same direction : muscular scars deep,
particularly that of the anterior adductor, which is pearshaped.
L. 1-8. E. 2-1.
Yar. albicla. Shell whitish and without coloured rays.
Habitat :
All our sandy coasts, from the Shetland to
the Channel Isles, from low-water mark to 55 fathoms.
Var. 1. Lerwick (Barlee and J. G. J.). This species is
fossil at Ayr (J. Smith), and in the Mammalian, Red, and
Coralline Crag (S.Wood). Nyst has recorded it from
the Belgian Crag, and Philippi from the Sicilian upper
tertiaries. It is not uncommon in the North Sea from
Drontheim (Sars) to the Bohuslan district (Loven and
Malm), and south of Great Britain from Normandy
(Bouchard-Chantereaux) to Gibraltar and the Gulf of
Tunis (M'Andrew and Deshayes), at depths varying from
8 to 35 fathoms.
Turton noticed that one of the valves is more convex
than the other ;
the inequality is not great, but very per-
ceptible. Independently of this character, and of its
being infinitely more common,
T. crassa differs from
T. balaustina in being at least six times the size, having
a more solid texture, and the ridges being stronger and
more compact; the fry are oval instead of triangular.
The one is the " porcelain of creation"; the other is
common ware.
According to Brown, the present species is the type