52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



R = 7-8 br. Rays more or less flattened, botli actinally and abactinally, tapering 

 abruptly to a blunt point so that the free portion is nearly triangular; the length 

 of the triangle is a little greater than the breadth, while the distance between the 

 tips of any two rays about equals the breadtli of a ray. Disc very large, somewhat 

 elevated at the centre but very gradually. Abactinal skeleton very stout with 

 small meshes. Whole abactinal surface covered more or less uniformly, but not 

 very thickly (15-20 per sq. cm.), with nearly cylindrical, rather stout spines, one to 

 two millimeters long. These spines are not usually capitate, but in some specimens 

 many of them are. On the margin of the disc and bases of the rays, the 

 spines show some tendency to arrangement in radial series witli three series to a 

 ray, but when this arrangement is most evident, the spines in each series are 

 not ceably few and those in the lateral series are very conspicuous. — Sides of ray 

 with one or two series of compressed spines. — Actinal surface much as in helian- 

 thus, but the interbrachial areas are more extensive and have numerous papulae. 

 Adambulacral and other spines more or less variable, not essentially or constantly 

 different from those of helianthus ; owing to the greater fusion of rays, and conse- 

 quent increase of the interbrachial areas, the series of spines outside the adambula- 

 cral extend further inward. Buccal depression and membrane as in helianthus. 

 Pedicellariae very small, both forficate and forcipate present, but the latter are 

 more abundant and are most abundant on rays abactinally. The pedicellariae are 

 infrequent, and often seem to be entirely wanting on the actinal surface. — Pedicels 

 in a zigzag row on each side of the ambulacrum, so crowded near middle of ray as 

 to be quite distinctly quadriserial there. — Madreporite as in helianthus. — Color of 

 abactinal surface deep bluish-black ; spines (at least at tip) light brown, yellow, 

 yellowish, or whitish ; actinal surface whitish or yellowish, with pedicels darker 

 than spines and papulae ; madreporite brownish or blackish. 



Range. — Hood's Island (Gray); Chatham Island (U. S. N. M); Abingdon 

 Island (U. S. N. M.); Albemarle Island (M. C. Z.) ; Charles Island (M. C. Z.). 

 — This species is confined to the Galapagos Archipelago, and apparently occurs 

 throughout the group. 



Remarks. — As the type of cumingii is lost, it would be impossible to decide to 

 what form that name ought to be applied, were it not that the locality given by 

 Gray, with his brief description, leaves no doubt that the short-rayed Heliaster of 

 the Galapagos is the species he had before him. As Gray's description is so brief, 

 it was very natural that Verrill (1867) should say of his Peruvian specimens that 

 they " are, perhaps, the species described by Gray." When Peruvian and Gala- 

 pagian specimens are laid side by side, however, the difference between them is 

 usually very noticeable, and, as previously stated, I have felt justified in calling 

 them by different names, for the following reasons : — (1) The differences between 

 them are obvious and uniformly associated with locality. (2) These differences 

 are quite constant, and connecting forms are wanting or very rare. (3) The 

 geographical isolation of the Galapagian form is very complete, Heliaster being so 

 exclusively littoral. (I) In no other way can the differentiation of the Gala- 

 pagian Heliasters be so well emphasized. Nevertheless it is freely admitted that 

 there is room for difference of opinion as to the wisdom of this course, for the 

 probable existence of connecting links among Galapagian specimens would cause 



