REPORT ON THE ASTEROIDEA. 31 



above ; the breadth of the plates is less than the length or height ; and they form a well- 

 rounded lateral wall to the rays and disk. Each plate bears a short, delicate, cylindrical 

 and tapering spinelet, only a trifle more than a millimetre in length midway along the 

 ray, placed on the abactinal side of the rounding and directed more or less upwards and 

 at a slight angle outwards and aborally. The rest of the plate is covered with very small 

 papilliform spinelets, of uniform size and widely spaced. 



The infero-marginal plates are subequal in height to the companion series, with which 

 they alternate rather than stand opposed ; and their breadth on the actinal surface is greater 

 than their length. Each plate bears a short, delicate lateral spine, similar to, but rather 

 longer than, that on the supero-marginal series, directed horizontally and at a slight angle 

 aborally. The longest measures about 175 mm.; and the length diminishes towards the 

 extremity of the ray. On the inner half of the ray there is a second small spinelet, half 

 the length and size of the lateral spine, standing close behind it in the median line, and 

 occasionally another still smaller. On the outer part of the ray these small spinelets do not 

 appear to be developed ; and even on the inner part of the ray, plates occur in which they 

 are scarcely distinguishable from the general miliary spinulation of the plate. This con- 

 sists of minute, slightly tapering, thorn-like spinelets, of uniform size and widely spaced. 



The adambulacral plates have an acute angular projection into the furrow ; their 

 breadth is greater than their length ; and successive plates are rather widely separate, with 

 the intervening space filled by ligament. The armature consists of: — (1.) A furrow series 

 of seven to nine short, delicate, tapering spinelets ; the median one, which occupies the apes 

 or point of the angular projection, is the longest, and the others decrease as they recede from 

 it on each side. (2.) A superficial series on the actinal surface of the plate, consisting 

 usually of two, and occasionally three, short tapering spinelets, one longer and more robust 

 than the others. These stand in a slightly oblique line, transverse to the direction of the 

 ray. In small specimens and on the outer part of the ray the second and third spinelet 

 may be greatly reduced in size or aborted altogether, but usually a representative miliary 

 is present. One to. three very small miliary spinelets may also stand on the actinal surface 

 of the plate along its adoral margin, forming an apparent continuation of the furrow series ; 

 and occasionally one on the aboral margin, likewise in series with the marginal spinelets ; 

 and, more rarely, one on the outer margin behind the actinal spines. No other spinelets 

 are present on the plate. 



The mouth-plates are broad and the united pair convex and subtubercular, with a wide 

 semicircular free margin. Each plate bears seven small mouth-spines, the innermost longest 

 and most robust, the rest diminishing in size step by step as they recede from it. The 

 innermost spine of each plate is directed horizontally over the buccal membrane parallel 

 to the median interradial line, each succeeding spine radiating slightly more outward, 

 the small outermost spines of the series having also a slightly downward trend. On the 

 actinal surface of each plate there is a lineal series of four to six small spinelets running 



