Pvn H,i I'UitlS

360 VENERID.E.
are more strongly pectinated on the inner than on the outer
surface : palps very small for the size of the animal, triangular,
and striated like the branchial laminae : foot large, white, mus-
cular, lanceolate, bent, and furnished with a byssal groove.
Shell having a general resemblance to T. puUastra, but
distinguishable by the following characters. It is usually not so
convex, and less broad (or shorter from one end to the other) :
sculpture much coarser, the longitudinal striae being quite as
strong as the transverse ribs and often more raised the surface
;
is thus reticulated, and marked (especially on the posterior
side) by
rows of tubercles : colour of a more sombre and
uniform hue, mostly yellowish and variegated with rays and
zigzag streaks or spots of dark or light brown : dorsal margin
more straight and the posterior slope decidedly truncate.
L. 1-75. B. 2.
Var. quadrangula. Shell smaller, square-shaped, and more
convex.
Habitat :
Muddy gravel and sand at low-water mark,
with T. pullastra, on the shores of our southern and
western counties, Wales, and Ireland. Cheshire coast
(Hall) ; Scarborough (Bean) ; Northumberland and
Durham (Alder) ;
Berwick (Johnston and Maclaurin) ;
Clyde district (Eyton); Oban (J. G. J.); Sound of
Iona (Bedford) ; Skye (Forbes) ; Aberdeen (Macgil-
f
livray) Shetland ; (Forbes and M Andrew).
Var.
Cork (Humphreys); Bantry Bay (Barlee). This species
is subfossil in the Loch of Spynie, and in the
" Kjokkenmoddings," Morayshire (Gordon) : fossil in
the Scotch glacial beds (Smith) ; Belfast " alluvial "
deposit (Hyndman and Grainger) ; Sussex tertiaries
(Godwin-Austen) .
It also occurs with shells of Arctic
species in the newer pliocene strata of Bohuslan (Malm),
Uddevalla (J. G. J.), and Christiania (Sars) ; and with
shells of southern species in the Sicilian tertiaries (Philippi).
It has not been noticed in a living or recent
state by any writer on the northern or Scandinavian