Fam. 1, Plate 26. 



IDALIA ASPERSA, Alder and Hancock. 



I. flavida, fulvo et brunneo aspersa : appendicibns tentacularibus longis, ad basin utrique tenta- 

 culi 2, filamentis linearibus utrinque dorsi 4 ; brancbiis 12, parvis, stellatis. 



Hab. 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 pro- 

 duced, 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. It 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 ascer- 

 tain 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 per- 

 form 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. 



