Pvn H,i I'UitlS

PECTEX. 71
an inch long, and a trifle more than nine-tenths of an
inch in breadth. The stride in the present species are
raised and irregular ;
and they are never punctured or
reticulate. In the other species the striae are sunk or
impressed and regular, aud they are strongly punctured
or reticulate. The different substance of the shell, the
style and intensity of coloration, and the comparative
size of the left ear of the upper valve are also notable
marks of distinction. Even the fry of each species ex-
hibits its own peculiar characters.
It is the P. fuci of Gmeliu, P. reticulatus of Chem-
nitz, P. Landsburgi of Forbes, and P. aculeatus of my-
self.
8. P. si'milis *, Laskey.
P. similis, Lask. Mem. Wern. Soc. i. p. 387, t. viii. f. 8 ; F. & H. ii. p. 293,
pi. lii. f. 6, and (animal) pi. S. f. 1.
Body very variable in colour, often pale yellow or whitish
with brown streaks and blotches : mantle fawn-coloured with
patches and lines of orange and black : cirri short some ; are
white and others brown, a few being thicker and longer than
the rest and mottled with milk-white : ocelli 6-8 in front and
the former are
nearly twice as many in a second row behind ;
comparatively larger, pearly, and ringed with jet : foot
brilliant orange-colonr
or white.
of a
Shell nearly circular but expanding towards each side,
where it forms an obtuse angle, and rhomboidal behind in
consequence of the projection of the ears, equilateral, depressed,
extremely thin and rather glossy ; lower valve con-
siderably smaller than the other, and to some extent enclosed
within it : sculpture, fine and close-set concentric lines only:
colour yellowish or milk-white mottled with reddish-brown
or flake-white spots or streaks, and often marked by longitudinal
white rays or transverse zigzag lines of a Vandyke
pattern : margins very thin, semicircular in front and sloping
about halfway on each side at an angle of 45 degrees to the
beaks ; byssal slope not toothed or serrate : heals small but
* Like the fry of P. maxmius.