66 bulletin: museum of comparative zoology. 



the process will probably be found to be perfectly definite in Heliaster 

 also." 



The Relationships of Heliaster. 



So obvious are the resemblances between Heliaster and Asterias, that 

 such students of starfishes as Muller and Troschel (1842) and Liitken 

 (1872) declined to separate them generically and even Gray (1840 and 

 1866) only proposed Heliaster as a subgenus. Dujardin and Hupe 

 (1862) and Perrier (1875), however, considered the multiradiate forms 

 entitled to full generic rank, but very closely related to Asterias. 

 Viguier (1878), on making a careful study of the skeleton, reached the 

 conclusion that Heliaster is not only generically different from Asterias 

 but that it actually is entitled to rank as a family, distinct from the 

 Asteriidae, which he called the Heliasteridae. Since the publication of 

 his paper, Viguier's opinion has been almost uniformly adopted and the 

 Heliasteridae has been accepted as a natural family. The examination 

 of the large amount of material accessible to me has led me to feel that 

 the question needs to be reopened and the evidence re-examined. 



Viguier gave six characters upon which the family Heliasteridae is 

 based and we will consider them in the order in which he presents 

 them. 



1. The large number of rays, even more than in Pycnopodia. This is 

 an obvious and useful characteristic, but as Labidiaster has full as many 

 rays as those Heliasters which have the largest number ; as Pycnopodia 

 scarcely falls short of the Heliasters which have the smallest number ; 

 and as there is as great a difference between H. polybrachius and H. 

 kubiniji, as there is between the latter and Coscinasterias calamaria 

 (Gray), it does not seem as though much stress could be laid on this 

 point. 



2. The extended coalescence of the rays. This is also an obvious 

 character but it is not wholly confined to this genus for in some Asterids 

 such as Asterias ochracea Brandt (Plate 6, fig. 3) the fusion of the rays 

 is quite as great as in some Heliasters. Thus a specimen of A. ochracea 

 with R = 100 mm. has only 71 mm. free which is practically the same 

 proportion as in some specimens of H. multiradiatus. Clearly this 

 character is not altogether distinctive. 



3. The separation of the rays by very strong, true interbrachial walls. 

 This is probably the best character of which Viguier speaks, for such 

 starfishes with numerous rays as Labidiaster and Pycnopodia, have no 

 true interbrachial walls. It should be pointed out however that the 



