444 DESCRIPTIONS OP SPECIES OF HELIASTER. 



Other described species of tlie genus, in tlie cliaracter of the spines of 

 the abactiual surface. There are six specimens in the collection, with 

 from 24 to 37 rays each, the larger specimens having from 35 to 37 rays. 



In one of the largest specimens, the longest radius measures about 

 75mm. tlie diameter of the disk, about GO"^'"; the entire length of the 

 rays, about 48">'" ; and the length of the free rays, from 12'"'^ to 16""^. 

 A small specimen affords the following measurements: longest radius, 

 about 40'""' ; diameter of disk, 28""" ; entire length of rays, about 28""" ; 

 length of free rays, from 10""" to 15""". In the largest specimen the 

 free rays are somewhat conical in shape and taper rapidly to subacute 

 points; in a second large one, and in the smaller ones, they are rather 

 more elongate and slender proportionally, and taper less rapidly. They 

 do not in any cMse diifer sufficiently from those of H. viicrohrachia to 

 furnish characters to distinguish tbese two species. The igrooves be- 

 tween the united portions of the rays are very shallow and narrow, 

 sometimes existing as mere creases, but are generally distinct. The 

 limits of the disk are not more plainly marked than in H. onicrobracJiia, 

 but the specimens in the collection are rather more convex or inflated, 

 due probably to their being better preserved. 



Tne spines are of nearly uniform size and shape over the entire abac- 

 final surface, excepting towards the tips of the rays, where tbey are 

 smaller. They are larger and much more widely and regularly distrib- 

 uted than in E. microhmchia, aud have a more regular arrangement thau 

 in n. muUiracUata, in which tliey are equally large. The large and small 

 specimens differ widely in the shape of the spines. In the former they 

 are stout, mostly subcorneal or tooth-like in shape, blunt and rounded 

 at the tips, though probably acute when not worn. Some of the spines, 

 however, are short, cyhndrical, or preserve nearly the same thickness 

 throughout. They measure about 2.5"'™ in length, about 1™™, or 

 slightly more in greatest diameter, and are placed from 2 to 5™"^ apart. 

 In the younger specimens they are much shorter and proportionally 

 stouter, smallest at the base, and becoming enlarged or inflated and reg- 

 ularly rounded above, being decidedly bead-like in appearance. They 

 are usually smallest over the median portion of the disk, where they are 

 also more slender than elsewhere, and upon the outer part of the rays. 

 As in the other species of the genus, there is no special arrangement of 

 the spines upon the disk, but they are very regularly distributed, much 

 more so than in the other species. Outside of the disk, in the larger 

 specimens, they form more or less regular, radiating rows, three to each 

 ray, the lateral rows bordering close upon the narrow grooves, and on 

 the free ])orti()ns of the rays extending rather far down upon the sides. 

 The median row is entirely regular and single in one specimen, but in 

 another it continues so for only about one-half the length of the rays 

 from the disk, whence to ne:w the tip, it forms an irregular series, two 

 or three spines in width. The smaller spines toward the ends of the 

 rays bear some resemblance to those of the young specimens above de- 



