162 



NATURAL HISTORY BULLETIN 



unequal spines side by side ; the larger one is on the aboral side 

 of the plate, and similar in form to the outer of the furrow- 

 spines, but somewhat larger; the smaller one is more spatulate 

 at the tip, and not quite so long. The outer end of the plate 

 bears a marginal group of five to seven, most often six, small, 

 spatulate, divergent spines, which often form a stellate group, 

 but in other states of preservation seem rather to form two 

 radial rows of about three each, not very regularly placed. Rare- 

 ly a short ovate pedicellaria replaces part of these spinules. 



The peroral spines are numerous and rather stout ; epioral are 

 very numerous and crowded, small, spatulate and flat at the tip. 

 Color of the dry specimen yellowish brown. The colors, in life, 

 are variable. It is often orange. It may be purplish on the 

 paxillar area, orange-red on the superomarginal plates, with the 

 marginal spines purple, and lower surface yellow. 



Variations. 



This is known to be a variable species. The superomarginal 

 plates vary in prominence and size, and their small conical spines 

 may be reduced to tubercles, and disappear irregularly on more 

 or less of the distal plates, or even be entirely lacking. In other 

 cases they extend to the interradial plates. 



The marginal spines of the inferomarginal plates may be less 

 flattened, and more acute than in the one described above, espe- 

 cially on young specimens. The flat, scale-like spinules of their 

 lower surface may be less flat and more slender. The inner 

 adambulacral spines, in the young, may be much more slender 

 and less flattened, and the same is true of the outer ones. Pedi- 

 cellarige, of rather small size, occur rarely. 



The young. A young specimen from oif St. Martine Reef, 

 West Florida (No. 16,322, U. S. N. Mus.) with the radii 10"^ 

 and SO^'"' has all the essential characters of the adult, but the 

 small dorsal marginal spinules are not developed on the first five 

 or six plates. Center of disk has a low cone. 



A still younger specimen (No. 16,324, U. S. N. Mus.) from 

 Cape Romanes, Fla., has most of the characters of the adult. 

 Its small dorsal marginal spines extend, on most of the rays, to 

 the fourth proximal plate. 



There is a central conical elevation of the disk, with a minute 



