REPORT ON THE ASTEROIDEA. 77 



6. Dy taster biserialis, n. sp. (PI. X. figs. 3^and 4^; PL XIII. figs. 3 and 4). 



Rays five. E = 44 mm. ; r — 10 mm. R < 4 - 5 r. Breadth of a ray near the base, 

 8 '5 mm. 



Kays elongate, narrow and tapering; of a more or less rigid habit, comparatively 

 thick, subquadrate in section, with vertical lateral walls. Interbrachial arcs widely 

 rounded. Abactinal surface plane and level. Actinal surface of disk convex, prominent 

 at the mouth-angles, and sloping thence to the margin and slightly along the ray. 



The paxillse of the abactinal surface are very small, simple, and crowded, normally 

 composed of four short papilliform or almost granuliform spinelets ; often three only are 

 found, and five are but rarely present. They are devoid of a central spinelet or granule. 

 On the outer half of the ray the paxillse are quite microscopic, more widely spaced, and their 

 simplicity is more evident. On the disk and at the base of the rays a great number of 

 paxillse are metamorphosed into pedicellarke, the three or four constituent spinelets being 

 much enlarged, modified in form, and so placed that the tips are brought together, thus 

 forming a large and powerful trivalvate or quadrivalvate pedicellaria. These form a con- 

 spicuous feature on the abactinal area, and their distribution amongst the paxillse is 

 irregular. The pedicle of the paxilla consists of a general tubercular convexity of 

 the plate. 



The supero-marginal plates, twenty-eight in number from the median interradial line to 

 the extremity, form a narrow and more or less bevelled margin to the rays, the breadth being 

 less than the height or the length, and the latter dimension is slightly the greatest. The 

 series of plates form a continuous level surface, uninterrupted by individual convexities. 

 Each plate bears a short, conical, but blunt spinelet, little more than an elongate tubercle, 

 placed on the curved part of the plate and directed at an angle outwards. The surface 

 of the plate is covered with very minute, widely spaced conical granules. 



The infero-marginal plates correspond exactly to the superior series, each being directly 

 beneath and opposite its companion plate ; their line of suture is consequently straight. 

 The breadth on the inner part of the ray is a little greater than the length, but on the 

 outer part the proportions are reversed. Each plate bears a single short spinelet similar 

 in size and character to those on the supero-marginal plates, or perhaps a shade longer ; 

 and the surface of the plate is covered with similar minute, conical, widely spaced granules. 



The adambulacral plates are long and very narrow, and with the furrow margin only 

 slightly convex. Their armature consists of : — (1.) A furrow series of eight short, cylin- 

 drical spinelets, the outermost on each side being shorter than the rest. (2.) Immediate!}* 

 behind the furrow series is a lineal series of six similar but rather smaller spinelets, 

 running parallel to the median line of the ray. On the outer part of the ray the 

 spinelets of both series become extremely short. No other spinelets or granules are 

 present on the plates. 



The mouth-plates are large, elongate, narrow,, and the united pair are prominently 



