REPOET ON THE ASTEKOIDEA. 39 



defined longitudinal lines maybe distinguished; their presence amongst the small and 

 comparatively inconspicuous general paxillse of the abactinal surface forms a striking 

 feature in the species. 



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

 extremity, form a well-defined though rather narrow border to the rays. The breadth, 

 height, and length are about subequal, the last dimension being slightly in excess, and the 

 plates are slightly convex and subtubercular abactinally. Each plate bears a robust, conical, 

 tapering spine, about 4 mm. in length midway along the ray, directed perpendicularly to the 

 abactinal plane of the ray. These spines diminish a trifle in length as they approach the 

 base of the ray, but increase in robustness ; whilst they decrease both in length and 

 robustness on the outer part of the ray. On the outer side of this spine is usually a smaller 

 and more delicate spinelet directed outward at an angle of about 45°, and occasionally 

 two may be present, and sometimes they are little more than elongate miliary spinelets. 

 The rest of the plate is covered with numerous very short, delicate, pointed miliary 

 thornlets. 



The infero-marginal plates alternate with the superior series, and their dimensions are 

 subequal. Each plate bears three robust, conical, tapering, pointed spines, similar to those 

 on the supero-marginal plates. These spines form a series along the median transverse 

 line of the plate ; the outermost or lateral spine is the longest, and slightly greater than 

 the supero-marginal spine ; the innermost spine of the three is the smallest, and is about 

 half the length of the lateral one. The longest lateral spine is the third or fourth 

 from the interradial line, and measures about 5 mm., and the succeeding ones decrease 

 slightly in length as they proceed outward. The rest of the plate bears a few widely 

 spaced, small, miliary thornlets, some of which at the base of the large spines are more 

 elongate than the others. There is a naked suture-line between each plate. 



The adambulacral plates are slightly longer than broad, and with only a slightly convex 

 margin towards the furrow. Their armature consists of : — (1.) A furrow series of six short, 

 rather thick, cylindrical, obtusely pointed spinelets, the inner pair slightly longer, and 

 the outer one at each extremity very much smaller, than the rest ; their posture resembles 

 that of the fingers of a hand held slightly concave. (2.) On the actinal surface of the 

 plate are two robust, slightly tapering but obtusely pointed spinelets, one behind the other 

 in the transverse median line. The innermost stands close behind the marginal series, the 

 outermost is slightly larger and is subequal in size to the innermost of the three spines on 

 the infero-marginal plate. Two or three minute miliary spinelets may be present on the 

 outer margin of the plate, but the rest of the plate has a naked appearance, and is only 

 covered with membrane. 



The mouth-plates are powerful and slightly convex ; each plate of the united pair 

 bears on its free margin six mouth-spines, the innermost being the longest, most robust, 

 and slightly compressed ; the others decrease as they recede from the mouth and become 



