SPINTHER ONISCOIDES. 231 



it has been met with in the Bay of Fundy, New Brunswick, by Stimpson and Leidy, and 

 at Station 275 (Ost Havet) den Norske Nordhavs-Expedition 1876-8 (Hansen). Verrill 

 includes it in his list of marine forms from Cape Cod to the St. Lawrence. 



Body. — Length 11 to 26 mm., the British forms seen by Johnston approaching the 

 first-mentioned figure, ovate or somewhat oblong, convex dorsally, smoothly rounded at 

 each extremity. The more convex dorsum has a series of symmetrical double lamellae, 

 strengthened by simple or bifid bristles, the tips of which slightly project beyond the 

 skin, these lamellae being continuous with the feet, which in Von Graff's example amounted 

 to forty-eight, Johnston's specimens, apparently having fewer. The ventral surface ha s 

 a series of low ridges studded with minute warts, the anterior sloping forward and the 

 posterior backward, the middle line being marked by a furrow, likewise warty. In the 

 largest example (26 mm.) the thickness in the centre of the body was 2*5 mm., thinning 

 off at the sides, and the breadth about 11 mm. ; the height of the dorsal lamellae in the 

 same being 1*5 mm. The anus terminates some distance within the posterior border, the 

 adjoining pair of ventral ridges presenting no special differentiation. 



Colour. — Johnston's examples were of a uniform cream-yellow colour, while Von 

 Graff's had a yellowish-ochre hue. Stimpson observes that his specimen was of a 

 beautiful lemon-yellow colour, resembling very much that of some sponges occurring 

 with it on a gravelly and muddy bottom in thirty-five fathoms in Hake Bay, Grand 

 Man an. 



Read. — This region is merged into the general contour of the body, but bears 

 superiorly over the brain the ridge-like dorsal tentacle with four eyes at the base. The 

 mouth opens on the ventral surface some distance behind the anterior border, often as a 

 radiate button — from the protrusion of the proboscis. 



Feet (parapodia). — These are distinguished by the possession of a ringed base, and 

 the presence of a short dorsal cirrus of about four or five segments, the lamellar ridge of 

 the dorsum curving smoothly away from it on the one hand, while on the other the 

 golden hooks emerge near its base ventrally. The hooks, which are excellently figured 

 by Von Graff, 1 have strongly curved and sharp points, while the terminal process of the 

 shaft is boldly serrated. One or two of these project freely, while internally one or two 

 are in course of development, the point appearing first, according to Von Graff, in a 

 cellular matrix. 



It is remarkable that, notwithstanding the great increase of zoological explorations 

 of the British seas, no example of this species has been procured since Dr. Johnston 

 described it, with fair accuracy — both with regard to external form and the characters of 

 the bristles and hooks — from two examples forwarded by Mr. Wm. Thompson of Belfast. 

 Moreover, Prof. Jeffrey Bell informs me the type specimens cannot be found in the 

 British Museum. Under these circumstances the only alternative was to utilise what 

 had been so ably written by Von Graff and others, and place materials for ready 

 identification in the hands of future observers. 



The species follows the habit of certain marine forms, adhering to sponges and 

 feeding on them, so that the alimentary canal, including the dorsal blind sac, is packed 

 with sponge-debris and spicules. 



1 Op. cit., pi. viii, figs. 4 and 5. 



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