264 MB. W. PEROT SLADEN ON THE 



portion to a pointed extremity. Interbracliial angles rounded. 

 Breadth of a ray at the base 6-25 millim. 



Supero-margiual plates small, about 23 in number from the 

 interbrachial angle to the tip, higher than broad, not tumid, form- 

 ing an even and well-rounded margin to the ray ; the extension 

 on the dorsal surface small, consequent on the narrowness of the 

 plates. The surface of the plates is covered with large, flat- 

 topped, well-spaced granules, which diminish a little in size at 

 the margins ; and the suture or furrow between neighbouring 

 plates is almost hidden. The usual fine cilia, if present, are en- 

 tirely concealed. No spinelets or tubercles of any kind are borne 

 on the supero-margiual plates. 



Infero-marginal plates much broader than high, do not extend 

 beyond the superior series, and have a sharp subangular rounding 

 on to the actinal surface. Each plate bears a single marginal 

 spine, and no other spines are present, the whole surface 

 of the plate being covered with moderately well-spaced, small, 

 flat, subacuminate squamules very little longer than broad. Two 

 of the squamules immediately behind the marginal spines are 

 longer than the rest and subspiniform. There is no tendency to 

 spinulation on any other part of the plate. The marginal spines 

 are short, delicate, subcylindrical, slightly compressed, tapering 

 from the base to a very finely pointed extremity, and are very 

 faintly curved : they are directed horizontally from the ray at 

 right angles to the axis, and are wide apart ; those in the middle 

 of the ray are slightly longer than the others, which decrease in 

 length towards the inner and outer portions of the ray; the longest 

 spines are nearly equal to the length of three infero-marginal 

 plates. Not more than two or three ventral plates are present, 

 and these carry small papillose spinelets forming an incipient 

 pedicellaria-like group. 



Ambulacral spines short and rather robust, forming two distinct 

 series, three in each. The inner series consists of three short, 

 robust, obtusely-tipped spinelets, radiating apart and arching 

 over the furrow, the middle spine longest. The outer series of 

 three spines are much shorter than the inner series ; the middle 

 spinelet slightly longest and twice as robust as its companions, 

 this spinelet having a short, flat, subspatulate form. The aboral 

 spinelet is smallest and is placed in advance of the other two, its 

 position almost suggesting that it ought to be reckoned as be- 

 longing to a middle series, an idea which is further strengthened 



