CLARK : THE STARFISHES OF THE GENUS IIELIASTER. 55 



tinal surface dull greenish, blackish, or black, often variegated with yellowish 

 blotches ; sometimes the appearance is that of a yellowish background with a few 

 small blackish blotches ; spines and actinal surface yellowish ; pedicels and mad- 

 reporite brownish. 



Kange.— Zorritos, Peru (Verrill) ; Payta, Peru (M. 0. Z.) ; Chili (M. C. Z). 



— The distribution of this species seems to be curiously limited, for while it ap- 

 pears to be very common at Payta, Zorritos is the only other port from which it is 

 recorded. Aside from the specimens from Payta, there is a single poor and old 

 specimen in the Museum of Comparative Zoology labelled " Chili," but nothing 

 further is known of its origin. 



Remarks. — The differences between this species and the preceding may be 

 briefly summarized as follows : — In polybrachius the rays are more numerous, 

 averaging more than 37 as against 35.6 in cumingii, and the free portion is 

 shorter, stouter, and more bluntly pointed; the abactinal spines are much 

 more numerous (25-50 per sq. cm. where thickest), lower and more capitate, 

 and pedicellariae are usually abundant on the actinal surface, while in cumingii 

 they are often wanting ; the color of polybrachius is often lighter than that of 

 cumingii, and the Peruvian specimens are frequently variegated abactinally with 

 yellowish. The most obvious of these differences are well brought out in the 

 figures given on plate 2. Doubtless there is room for wide difference of opinion 

 as to the significance of these differences, and whether they are important enough 

 to entitle the Peruvian form to a separate name. There are three possible courses, 

 any one of which we might follow : — (1) We might call the Peruvian specimens 

 cumingii, and simply point out the features in which they differ from Galapagian 

 specimens ; (2) we might call them a subspecies of cumingii, and make use of a 

 trinomial name for them ; (3) we might regard them as a distinct species. I 

 have already given (p. 52) the reasons which lead me to consider the third of these 

 possible courses the best, but I am free to admit that 'polybrachius and ctcmingii 

 are so closely related that were they both found on the same coast I should con- 

 sider it unwise to attempt to separate them. It seems to me clear, however, that 

 one is an offshoot of the other, and the facts already given under cumingii with 

 reference to the variability of the island specimens seem to show that that 

 species is the offshoot from polybrachius, as the geographical distribution of the 

 two forms would lead us to expect. The offshoot, however, is the one which has 

 borne a name for over sixty years, while the parent stock has remained nameless. 

 In selecting a name for it polybrachius has been chosen because the average num- 

 ber of rays is greater than in any other species of Heliaster. 



Material examined : — 



51 specimens. Payta, Peru. M. C. Z. Collection. 

 1 specimen. " Peru." " " 



1 " "Chili." " " 



53 specimens. 3 localities. 



