CLARK : THE STARFISHES OF THE GENUS HELIASTER. 67 



beginnings of just such walls as occur in Heliaster are to be seen in 

 Coscinasterias calamaria (Gray) (Plate 6, fig. 2) and they are well 

 developed in Asterias ochracea Brandt (Plate 6, fig. 3). Consequently 

 too much importance must not he attached to this feature. 



4. The position of the mouth at the bottom of a sort of funnel. The 

 value of this character is an open question but there is no reason for 

 supposing it has any great significance as a structural feature. It is 

 nearly or quite wanting in many individuals, although the best preserved 

 specimens show it more or less clearly. Even if it were always present 

 in normal living individuals, it could hardly be considered of sufficient 

 importance to be a family character. 



5. The fragmentation of the madreporite. Although the madreporite 

 of an adult H. helianthus is usually fragmented, and although the same is 

 true of the other forms with more than 30 rays, yet in young specimens 

 of these species and in adults of hubiniji and multiradiatus such is not 

 the case, but the madrepoi'ite is, on the contrary, exactly as it is in 

 Asterias, simple and convex. The condition of the madreporite cannot 

 then be used even as a generic character. 



6. Tlie peculiar and remarkable farm of the odontophore. In regard 

 to this point, there is room for difference of opinion, for while no one 

 questions the interesting fact which Viguier emphasizes that the basal 

 mterbrachial plate (or "odontophore " as he calls it) is fused in Heliaster 

 with a larger interbrachial plate behind it, it is difficult to determine 

 how much value such a character has from a taxonomic point of view. 

 Sladen (1889) holds that it has little or no value and that greater 

 differences in this plate may occur between closely allied species than 

 between other species of quite different genera, so much depends on the 

 number of rays and the character of the adambulacral plates. Careful 

 comparative study of the actinal skeleton of Asterias and Heliaster leads 

 me to believe that Sladen is quite right and that we cannot place any 

 exceptional weight on peculiarities in this so-called " odontophore." 



The characteristic features of the family Heliasteridae, then, as given 

 by Viguier, do not seem to bear close examination, and fail to prove of 

 sufficient constancy and distinctiveness to warrant the separation of the 

 genus Heliaster from the Asteriidae. Before the matter is considered 

 settled, however, there are other points to be examined which will 

 throw some light on the subject. It is remarkable that Viguier fails to 

 mention the conspicuous discobrachial wall of Heliaster (Plate 6, fig. 1), 

 for there is no other feature of the anatomy which is so characteristic of 

 the genus. It is quite possible that, with the small amount of material 



