Pvn H,i I'UitlS

TELLTNA. 379
4. T. te'nuis * Da Costa.
T. tenuis, Da Costa, Brit. Conch, p. 210; F. &H. i. p. 300, pi. six. f.8,
and (animal) pi. K. f. 3.
Body very flat, yellowish-white : mantle : finely fringed tubes
white, nearly equal in length and diameter, the upper one
being usually curved upwards :
gills two only, one on each side,
veiy large and membranous, nearly triangular, most delicately
pectinated, and pale brown : palps triangular, not very long or
pointed, nor so disproportionately large as in the last species,
pectinated more strongly inside than outside, of a sombre hue,
marked with paler lines which give them a mottled appearance
: foot large, broad, compressed, not very pointed, slightly
bent.
Shell triangularly oval, flattened, thin, semitransparent,
remarkably glossy and polished ; the right valve is a trifle
and indistinct
larger than the left : sculpture, exceedingly slight
concentric strise, with occasional deeper lines of growth ;
surface is also marked with a few short and obscure longitu-
dinal lines : colour white, yellow, flesh, orange, pink, or rose,
of various shades, sometimes whitish with a large rosy mark
on the umbonal area, or with two divergent streaks of yellow
or pink, one on each side of the beaks, or pink with similar
whitish rays, or else with transverse bands of a deeper hue :
epidermis slight and brilliantly iridescent : margins generally
not much curved in front, more so and often bluntly angular
on the anterior side, somewhat flexuous on the posterior side
and produced to a rather sharp point, from which a slight
ridge runs to the beak in each valve, separating the posterior
area ; this margin is obliquely truncate ; the dorsal or ligamental
margin has a straight slope to the upper angle of the
posterior side : beaks small, nearly straight, scarcely inflected,
but turned towards the posterior side : ligament short, but
large, very prominent, light horncolour : hinge-line obtusely
angular :
hinge-plate much broader on the posterior than on
the other side, and abruptly truncate at the end of the ligament
: teeth, cardinals as in the last species sometimes the
;
left valve has a posterior, or the right an anterior lateral : in-
side glossy, having the same coloured markings as the outside,
microscopically wrinkled, and striated towards the margin :
pallial scar as in the last species : muscular scars oblong, large
and conspicuous. L. 0*65. B. 0-95.
* Thin.
the