240 ME, W. PEKOT SLADEir ON THE 



veloped, slender, round, and tapering but sliglitly . Interbrachial 

 angles very wide and expansiye, the curve sliglitly flattened in 

 tL.e immediate angle, thereby emphasizing the marked pentagonal jj] 



contour of the body-disk. The lesser radius is in the proper- |' 



tion of 42*5 per cent.; jB=20 raillim., r = 8"5 millim. Disk de- f 



pressed, not inflated ; both dorsal and actinal surfaces stand on | 



a level with the edges of the marginal plates. [ 



Dorsal area covered with closely crowded paxillse, the whole I 



disk as well as the base of the rays being uniformly packed. The f 



paxillse are very fine and small, and are made up of about 5 to \ 



10 spinelets; towards the margin of the disk they become smaller | 



and also in the centre, where they are very compact, a slightly ' 



prominent peak being formed as in Ctenodiscus. A slight eleva- 

 tion of the surface is present in the median radial line, opposite 

 the base of each ray, and at about one third of the distance from 

 the margin to the centre. 



Marginal plates occupy the entire margin and represent the 

 whole thickness of the animal, forming perpendicular walls re- 

 gularly rounded above and below. Along the rays the supero- 

 marginal plates meet in the median dorsal line and form a com- 

 plete casiag to the ray, which is well rounded, small, and tapers 

 but slightly. The supero-marginal series are 8 in number (or, 

 with a very small aborted one, 9), exclusive of the terminal. 

 The plates which fall in the margin of the disk proper have the 

 length about equal to their height, but in those along the ray 

 the height is greater than the length. The infero-marginal plates 

 correspond in number and in length with the superior series. 

 In the arm-angle, along the disk proper, the height is about 

 equal to the length and the plates are uniform in size with the 

 superior series ; towards the extremity of the ray the height 

 diminishes gradually and the length is greater than the height — a 

 reversal of the relative proportions presented by the plates of 

 the superior series. The marginal plates are smooth and bear 

 no spines, but when examined microscopically have the appearance 

 of being subgranular and built up of a rather open network. 

 The plates of both series are convex outwardly or tumid in a 

 very slight degree, by which means the sutural divisions of the 

 segments are clearly marked out, and a somewhat annulated ap- 

 pearance is given to the ray. The terminal plate is large and 

 conspicuous, appearing somewhat tubercular and dh-ected slightly 

 upwards when viewed in profile, and oval in contour when seen 



