EEPOKT ON THE ASTEKOIDEA. 273 



of the ray than by the regular curve of the side as a -whole. Margin thick and vertical, 

 equally rouuded actinally and abactinally. Actiual area plane or slightly concave, undu- 

 lating, more or less flexible, and capable of some inflation ; a slight sulcus usually defined 

 along the median interradial line. 



The whole abactinal area is covered with small, regular, polygonal tabula, which 

 diminish in size as they approach the margin (where they are very small) ; they are also 

 smaller in the central region of the disk and along the edge of the interradial sulcus than 

 in the median radial area and on the actual floor of the sulcus. The larger tabula in the 

 radial areas, which are more or less elevated or paxilliform, are comparatively widely 

 spaced, exposing the papulae, of which there are about six round each tabulum, separated 

 from one another by the stellate prolongations of the basal portion of the plates. The 

 paxilke consist of a hexagonal, rhomboid, or polygonal tabulum, slightly raised and 

 faintly convex in the radial regions, where the paxillse are widely spaced. The tabulum 

 is covered with coarse, low, and almost truncate granules, and the margin is surrounded 

 by a series of thin lamelliform papillae or flattened granules, which have a striking appear- 

 ance as compared with other species (see PI. XLIX. fig. 1). A small excavate pedicellaria 

 with two rather broad jaws and associated pit is present on some of the tabula, and 

 appears to be always placed at the margin of the tabulum, some of the neighbouring 

 granules being scooped away as it were for its reception. 



The supero-marginal plates, which are seventeen in number, counting from the median 

 interradial line to the extremity, form a well-defined and nearly uniformly broad border to 

 the abactinal area. The plates near the interradial line have their length and breadth 

 subequal, the length being perhaps slightly in excess ; as they proceed along the 

 ray, however, the length diminishes step by step, until at the extremity the breadth is 

 fully twice as great as the length. The plates are distinctly tumid. The lateral surface 

 of the plates is covered with very small, uniform, crowded granules, but on the abactinal 

 area of the plate there is a large naked quadrangular space which occupies nearly the 

 whole of that surface, being separated from the margin only by two (or rarely three) rows 

 of the small granules. The majority of the plates bear one, or occasionally two, small 

 pedicellarise placed at the edge of the naked space. 



The infero-marginal plates correspond to the superior series, and are, like them, 

 covered with small crowded granules, excepting, however, a small circular area on the 

 actinal surface of each plate, which is naked. Nearly all the infero-marginal plates bear 

 one of the small excavate pedicellariaa similar to those on the supero-marginal plates ; a 

 few plates bear two. The pedicellaria? appear to be invariably placed close to one of the 

 margins of the plate. 



The adambulacral plates are slightly broader than long, and their armature consists of a 

 marginal series of six short, subequal spinelets, excepting the adoral spine of the series, which 

 is smaller. The spinelets are thick and subprismatic or quadrangular in section, and have a 



(ZOOL. CHALL. EXP. — PART LI. — 1888.) 35 



