ON A NEW SPECIES OF OPHIURELLA. 



BY Tiros. WRIGHT, Esq., M.D., F.R.S., 6fc. 



GENUS OPHIUEELLA, Agassiz, 1836. 



|ISK small, membraneous, often indistinct, a character 

 wliicli separates this genus from Ophiura. Eays 

 very long, slender, depressed, formed of circles of 

 plates, four in each circle ; the lateral plates are the largest, 

 most prominent, and provided with long spines ; the basal plates 

 are small and spiniferous, and the dorsal smooth and without 

 clothing. Mouth plates small and triangular. All the species 

 known were found in the Jurassic rocks. 



OPHIUEELLA NEEEIDA, Wright, 1880, n.sp. 



Description. — Disk small, irregularly penta-lobed, each lobe 

 consisting of a shield-like elevation formed by the radial plates, 

 which are covered by a tegumentary membrane closely studded 

 over with small granules ; the inter-lobular integument is 

 entirely absent, having apparently, if it ever existed, been 

 destroyed in the process of fossilisation. 



The arms, or rays (five in number), are long, four times the 

 length of the disk's diameter. They do not taper much between 

 the radial plates and their termination, and consist of innumer- 

 able highly moveable rings, composed of : — 1st, a centre-dorsal 

 plate, which, with its fellows, form a long, smooth, convex, 

 continuous chain, flattened at the summit, and laid along the 

 middle of the rays ; 2nd, of lateral plates, which bend down- 

 wards, closely clasping the sides of the ray ; each plate supporting 

 a small tubercle, on which a stout thorn-like spine is articulated 



