J48 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



of them 0.5 mm. or less. The larger ones occur on the papular areas and are 

 rudimentary central spinules. There is great variation in their number, but they 

 arc never numerous and never extend very far upon ray, being about 1 mm. long. 



In some specimens abactinal pectinate pedicellariiB are about as numerous on 

 disk and rays as in acanthonotus, but on one example they are comparatively 

 scarce. Each comb consists of three to six short robust, blunt, spinelets, typically 

 much stouter and broader than in acanfJionotus. While most of the pedicellarise 

 consist of two combs there are some M-ith three, in which case each comb has few 

 spinelets. Far along ray the siiiiielets are very short and inconspicuous. 



Abactinal plates of papular areas much less distinctly lobed than in acantho- 

 notus. The larger plates are roundish with a few irregular slight projections. 

 The intermediate small plates are roundish on disk, but on ray more irregular 

 ^\'ith two or three lobes, or none. On papular areas the plates generally touch, 

 but on ray they become quite widely separated, especially on the median radial area. 

 Papulae confined to base of ray and disk, but are absent from the center of disk 

 and a narrow interradial line. They do not extend as far upon ray as its width at 

 base. 



Marginal plates thin, confined to side wall of ray, each superomarginal with 

 one stout tapering sharp spine, the inferomarginals on proximal part of ray with 

 two, on distal with one such spine. Of the two the lower is much smaller than the 

 other, which is about the same size as the corresponding superomarginal spine. 

 The general surface of plates is naked, but one to several additional small spinelets 

 occur on the plates of both series. Superomarginals, in type, forty-one. In the 

 type there is but one odd interradial superomarginal, the other four interradii 

 having paired superomarginals. The same specimen has three odd inferomarginals. 

 Tliis character is ver}' variable. One specimen has no odd superomarginal, and 

 two odd inferomarginals; another (otherwise not very tj'pical) has five otld supero- 

 marginals and three or four odd inferomarginals; another has three odd supero- 

 marginals; another, one. The interrarlial superomarginal (paired or unpaired) usu- 

 ally bears a stout spine and is raised higher than the rest, but when paired the 

 spine is frequently weak. 



Inferomarginal plates with a pcdicellaria on the vertical suture, these occurring 

 all along ray with now and then a suture lacking the apparatus. Proximally 

 each comb has eight or nine short, stubby, basally webbed papillae, winch soon 

 become five or six, and on the outer part of ray about three. 



Adambulacral plates with five or six blunt furrow spinelets and two much 

 larger, tapering actinal spines in a transverse series. The furrow spinelets are short 

 and the central oidy slightly longer than the laterals. 



Mouth plates with five or six marginal spinelets, of which all but the much 

 enlarged inner tooth are similar to though a trifle longer than the corresponding 

 adambulacral spinelet On the actinal surface is a linear series of four or five 

 longer spinules, not markedly different from those of B. spinosus. 



Actinal interradial areas fairly extensive for tins genus, \\ith one to four, or 

 without pectinate pcdicellaria?. Sometimes they are incomplete (^\^th one comb). 

 Each comb has three to seven blunt basally webbed papilliB or spinelets. The 



