40 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



cles). In two cases a half of a small fish was found in the stomach, but it is 

 probable that the fish were found dead on the rocks among the mollusks and 

 barnacles on which the Heliaster was feeding. — Parasitic gastropods (Sfj/lifer) 

 are common on specimens of Heliaster from the Galapagos Islands and occur not 

 infrequently on specimens from the South American coast. 



The following keys show the characters by which the seven species here 

 recognized are to be distinguished. The first is wholly morphological and shows 

 the species in what is probably their natural relationship. The second is quite 

 artificial and takes into account the geographical distribution ; it may be found 

 useful in identifying specimens from known localities, where a large series of in- 

 dividuals is not available for comparison. In using these keys, it must be borne 

 in mind that the number of rays is fewer in young individuals than in adults and 

 that (as already mentioned) they may be free for a much greater proportion of 

 their length. Consequently specimens under one hundred millimeters in diameter 

 cannot always be certainly identified by means of these keys alone. 



Key to the Species. 



A. Rays free for 30 per cent of their length, or more. 



B. Rays 30 or more, free about 35 (30-40) per cent of their 



length heliantkus 



B.B. Rays 28 or fewer, free for 40-70 per cent of their length. 



C. Spines on abactinal surface of disc numerous, little or 

 not at all capitate, smaller than those which form 

 conspicuous marginal series on abactinal surface of 

 rays ; between these marginal series is a median 

 series with a lateral series on each side ; latter gener- 

 ally inconspicuous and made up of very small spines ; 

 marginal series converge on disc, confining median 



series to ray canopus 



CC. Spines on abactinal surface of disc comparatively few, 

 many of them usually conspicuously capitate and 

 larger than those of marginal series of rays ; between 

 latter are three or more not very clearly denned series 

 of which the median is most conspicuous and con- 

 tinues inwardly onto the disc. 



Rays free for more than half their length, 50-70 per 

 cent ; color, abactinally, pale yellowish mottled with 

 blackish, the rays more or less distinctly banded; 

 spines, pedicellariae, and madrepore plate, light yel- 

 lowish multiradiatus 



Rays free usually for less than half their length, 

 40-55 per cent ; color, abactinally, deep purplish ; 

 spines, pedicellariae, and madrepore plate, more or less 

 deep yellow ; rays sometimes indistinctly banded . kubiniji 

 AA. Rays free for less than 30 per cent of their length, rarely less than 

 30 in number in adults. 



