OPHIURELLA. 



157 



studded over with small granules ; tlie interlobular integument is entirely absent, 

 having apparently, if it ever existed, been destroyed in the process of fossilisation. 



The arms, five in number, are long, four times the length of the diameter of the disk. 

 They do not taper much between the disk and their termination, and consist of innume- 

 rable highly moveable rings, composed of — 1st, a centro-dorsal plate, which with its 

 fellows form a long, smooth, convex, continuous chain, flattened at summit, and 

 laid along the middle of the rays ; 3nd, of lateral plates which bend downwards, clasping 

 closely the sides of the arms ; each of these lateral plates carries a small tubercle, on 

 which stout thorn-like spines are articulated by a kind of ball-and-socket joint; 3rd, 

 the ventral plates, which close in the ray below, are very much concealed ; and carry 

 many short stout spines. One of the spiniferous arms of this Ophiurella, as it lies on 

 the slab of Calcareous Grit before me, resembles a marine worm, the Nereis nuntia, and 

 hence the origin of the specific name I have ventured to give this new Brittle-star. The 

 arms are very much bent and curled, so that this species may be said to have had highly 

 moveable arms. 



Dimensions. — Diameter of the disk six tenths of an inch ; length of an arm two 

 inches and six tenths of an inch. This is less than they were in the living state, as none 

 of the arms are preserved up to their terminations. 



Affinities and Differences. — The fragmentary condition of the disk prevents any 

 definite conclusions as to the true generic position of this form, but it agrees with 

 Ophiurella closer than any other. It has the small disk with the upper and under 

 surfaces covered with fine granules ; the arms long, compressed, and flattened, the 

 lateral and ventral plates carrying spines, which are specially jointed to the lateral pieces. 

 In all these essential generic characters it agrees with Ophiurella. I know of no figured 

 species from the Corallian rocks that resembles our Brittle-star. The only form that 

 occurs to my mind is Ophiurella bispinosa, d'Orbig., which has only been named, but 

 was neither described nor figured by the author. Our species is so widely difi'erent from 

 all the other described forms that there can be no confusion with them. 



Locality and Strati^raphical Position. — This Brittle-star was obtained from the 

 Calciferous Grit at Sandsfoot Castle, Weymouth, by Professor Buckman, F.G.S., who 

 kindly sent it to me for a descriptive note of the species to be inserted in the ' Pro- 

 ceedings ' of the Dorset Natural History and Antiquarian Field Club. The figure was 

 drawn twice the natural size by Mr. Gawan, and has been engraved by Mr. H. P. Wood- 

 ward. The spines on the lateral plates are not so well shown in the figures as I could 

 have wished, as these spines form a very conspicuous feature in some parts of the rays. 

 Fig. 40 represents Ophiurella nereida as it lies on the slab, magnified twice the natural 

 size ; and Fig. 39 is a portion of one of the rays still more highly magnified to show the 

 arrangement and form of the dorsal and lateral plates of the arms. The specimen 

 belongs to Professor Buckman's collection. 



