(J4 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



The smaller spines are about 1 ."> mm. long by 0.5 or 0.6 mm. thick varying with their 

 position on disk and ray. 



Superomarginal plates rather low on the side of ray. Superomarginal spines a 

 little longer than the dorsolaterals and intermediate between these and the infero- 

 marginala which are decidedly stouter and longer. The superomarginals form a 

 vertical comb, or sometimes a group of three to five (occasionally six) to a plate the 

 median generally the largest. Their general form is clavate with a tapered, blunt, 

 sometimes compressed end, and the distal spines are faintly sulcated. The proximal 

 spines are sometimes "eroded" having a flattened area on the upper (and under) 

 side, converging, in some cases, into a sort of shallow groove on the distat part of 

 the spine. There is no well defined supramarginal channel although the series of 

 papular areas is here more regular on account of the regular series of superomarginal 

 plates. Intermarginal channel practically non-existent owing to the relatively small 

 size of the intermarginal papular areas and the heavy wreaths of pedicellariae which 

 pretty well fill up the channel. 



Inferomarginal spines conspicuously longer and stouter than the superomarginals, 

 two or three to a plate, clavate, more or less compressed, blunt to subtruncate and 

 frequently with definite eroded or sunken areas on the upper side of the spine. The 

 spines stand in an oblique series of two or a group of three. 



There are two series of actinal plates with a rudimentary third series at the base 

 of some of the rays. The spines, one or two to a plate, are very similar to the infero- 

 marginals, even a little heavier near the base of ray and some are quite definitely 

 subspatulate and truncate. The outer side is slightly concave as in the case of the 

 inferomarginals, this taking the form of a groove or of a sunken area. The whole 

 actinal surface has a very bristling appearance, and one may count from the upper 

 edge of the superomarginals to the adambulacral spines eight or nine spines, or in 

 exceptional instances one or two more. 



Adambulacral plates diplacanthid, and as is usual in such cases the slender furrow 

 spine of alternate plates stands further into the furrow than the stouter inner spine 

 of the intervening plate. In effect, the armature of alternate plates is set a little 

 more toward the outer edge of the plate. The spines are mostly terete, slender, 

 round-tipped, slightly tapered, or untapered, and many of them have a slightly 

 sunken area on the outer side near the tip, as in the case of the actinals. There 

 are four pairs of contiguous plates making up the adoral carina. On a few proximal 

 plates there are three spines. The spines lengthen toward the mouth plates, the 

 longest on the adoral carina (one to a plate) being about as long as the first five 

 adambulacral plates (6.5 mm.). 



The actinostome is very small. The oral armature consists of two heavy spatu- 

 late, round-tipped or subtruncato apical spines to each plate, and a cylindrical sub- 

 oral spine similar to the adambulacral spines. The larger, more median, of the two 

 apicals is nearly twice as long (4 mm.) as as the short plate, and its breadth varies 

 on the different plates. 



Papular areas smaller than the primary plates and with the distribution common 

 to the genus. The papulae are abundant and fill the spaces between the groups of 



-pllies. 



