Pvn H,i I'UitlS

396 TELLINID^.
3. P. Ferroensis *j Chemnitz.
Tettina Ferroensis, Chemn. Conch. Cab. vi. p. 99,
eizsis. F. & H. i.
p. 274, pi. xix. f. 3.
1. 10. f. 91. P. Ferro-
Body elongated, white or of the palest brown : mantle clothed
with a short white fringe, or rather with fine dentations : tubes
of nearly equal size and length ; the branchial is somewhat
the larger and longer, and when not fully extended it appears
finely corrugated and marked with two longitudinal bars, and
its orifice has six plain cirri; the excretal tube curves upwards,
and its orifice has no cirri :
gills and palps nearly as
and bevelled to a
in P. tellinella : foot very large, flat, long,
sharp edge.
Shell oblong and somewhat rhomboidal, compressed, rather
solid, opaque, more or less glossy when not covered by the
the right valve is usually larger than the other and
epidermis ;
slightly overlaps it : sculpture, numerous fine, but not raised,
concentric ridges, which are sharper on the anterior side and
often laminar or slightly imbricated on the posterior side, be-
sides minute and close-set parallel stria? in the interstices of
the ridges ; the surface is also covered with slight and indis-
tinct longitudinal or radiating lines, and the posterior slope or
area is often more or less marked with half a dozen slight
ribs, which radiate from the beaks and (especially in the
young) produce a cancellated and prickly appearance by their
intersecting the transverse ridges : colour beneath the epidermis
pink of different shades, diversified by longitudinal rays
of yellow or milk-white, some of which are broader than the
rest and frequently confluent or broken ; the surface also is
often marbled with short white lines or streaks ;
now and then
(but rarely) the colour is uniform purple : epidermis thick,
fibrous, more persistent than in either of the preceding species,
dusky in the adult and yellowish with a green tint in the
half-grown and young : margins not much rounded in front,
and occasionally almost straight, semioval, and wedge -like on
the anterior side, abruptly and obliquely truncate on the posterior
side, with an indentation or flexure on the ventral side
of the posterior angle ; a keel extends from the beak to this
angle, and the area thus separated is flat or depressed, and
sculptured by the radiating ribs above mentioned ; the dorsal
or ligamental margin is serrated in specimens strongly sculp-
* Belonging to the Faroe Isles.