OPHIURELLA. 
157 
studded over with small granules ; the 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 betvi^een 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 ; 2nd, 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 OpMurella, 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 
Ojjhiurella 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 OpMurella. I know of no figured 
species from the Corallian rocks that resembles our Brittle-star. The only form that 
occurs to my mind is Opldurella hispinosa, 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 Stratigrapliical 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 OpMurella nereida as it lies on the slab, magnified twice the natural 
size ; and Pig. 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. 
