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C. Hnlhnandei s Pa
IDALIA ASPERSA, A l d e r a n d H a n c o c k .
I. flavida, fulvo et brunneo aspersa: appendicibus tentacularibus longis, ad basin, utrique tenta-
culi 2, filamentis linearibus utrinqne dorsi 4 ; branchiis 12, parvis, stellatis.
Had. On a dead shell of Fusus antiquus from the fishing boats, Cullercoats.
Body half an inch long, thick, broadly elliptical, rounded in front, and abruptly tapering
to a point behind; of a yellowish hue, blotched and spotted above with reddish brown and
orange, which dies out towards the margin of the foot. The sides are sprinkled with opake
white. Tentacles two, placed upon the back a little less than one third of the length of the
animal from the anterior end; long, tapering, nearly linear, and much inclined backwards ;
of a fawn colour, freckled with brown and white. They are delicately laminated behind
from the top almost to the base; the front is smooth. At the base of the tentacles, and
nearly of the same length and thickness with them, are four linear, tapering, tentacular
filaments, one in front and another at the side of each tentacle. These appendages rest upon
a slight ridge, which is continued round the front of the tentacles and along the sides of the
back past the branchiae, terminating behind them. Upon this ridge, and about half way
from the tentacles, arise on each side four small linear filaments, the posterior ones longest
and situated at the sides of the branchiae. Branchice consisting of 12 short, stiff, simply
pinnate plumes with a broad mid rib, forming a complete circle round the vent, and non-
retractile. They are of a pale fawn colour,. speckled , with a darker shade of the same,
and with a large white patch near their apices. Behind these the back slopes rather
abruptly down towards the tail. Head broad and obtuse, slightly lobed, but not produced,
at the sides. The mouth is inferior; the ’margins of the lips as they pass off to the
sides are thickened in a peculiar manner, forming an arch at each side. Foot broad, rounded
and slightly arched in front, straightish at the sides, and abruptly brought to a sharp point
behind. I t is nearly colourless, the liver appearing through of a reddish salmon-colour.
A single specimen of this interesting addition to our fauna was obtained at Cullercoats
in October, 1844. It did not possess much activity, but, while moving about, its tentacular
filaments were kept perpetually in action. They waved with considerable grace, generally
from above downwards, and then, just tipping the ground, were flung up again as if to ascertain
the approach of danger. These might therefore be considered the true tentacles, did
not uniformity of nomenclature oblige us thus to designate the lamellated organs generally
considered so by naturalists. We have elsewhere endeavoured to show that the latter perform
a different function, yet perhaps not incompatible with their being also employed as
organs of touch.
In consequence of the position of the tentacles behind the cerebral ganglions, the eyes
in this species appear before the tentacles, and not in their usual position, behind them.