CLARK: THE STARFISHES OF THE GENUS HELIASTER. 45 



Heliaster canopus Perkier. 



Plate 3, Fig. 2 ; Plate 8, Fig. 7. 



Heliaster canopus Valenciennes. Perrier, 1875. 

 Heliaster canopus (Val.,MS.) Perrier. Sladen, 1889. 



There is no good reason why Valenciennes' name should be associated with this 

 species any longer, for his manuscript museum name has no standing. Perrier 

 was the first and only describer of the species. 



Description. — Rays, 20-27, averaging (27 individuals) 24; about 53 (47-60) per 

 cent of ray free. R — 30-60 mm. ; r = 15-30 mm. Breadth of ray at base, 4-7 

 mm. R = 7-8 br. Rays somewhat flattened, or a little arched abactinally, rather 

 angular, with blunt and rounded tips. Disc moderately large, flat, or a little 

 arched. Abactinal skeleton rather stout and with small meshes. Abactinal spines 

 numerous, small, rather slender, and not at all capitate, without definite arrange- 

 ment on disc, but appearing in distinct series on rays. Marginal series of ray con- 

 tain largest abactinal spines ; median series somewhat smaller. Between marginal 

 and median series, a lateral series of very small spines is often present. The 

 marginal series tend to converge as they pass on to the disc, and thus separate the 

 median and lateral rows from the spinulation of the disc ; this arrangement is usu- 

 ally evident, but is much more marked in some specimens than in others. — Sides 

 of ray with two or three series of long, compressed spines. Actinal surface essen- 

 tially as in helianthus. Pedicellariae fairly common, especially towards tip of rays 

 abactinally, chiefly forcipate ; large forficate ones rather rare and smaller than in 

 helianthus. Madreporite usually simple and convex, rarely flattened and frag- 

 mented. — Color of abactinal surface deep purplish-black ; spines whitish ; actinal 

 surface and madreporite yellow ; pedicels brownish-yellow. 



Range. — Juan Fernandez Islands (M. C. Z.). 



Remarks. — This interesting little species is remarkably well characterized, and 

 can be very readily distinguished at a glance. Perrier (1875) thought it possible 

 that it was the young of helianthus, but the large series of specimens collected by 

 the " Hassler " has made it possible to show that this is not the case. Young 

 specimens of helianthus have more than 30 rays by the time they are 70 mm. in 

 diameter, whereas the largest specimen of canopus, 120 mm. in diameter, has only 

 20, and there is only one specimen with as many as 27- The difference between 

 canopus and a young helianthus in the abactinal spinulation is well shown on 

 plate 3. Finally, it is important to note that in the larger specimens of canopus 

 the reproductive organs are fully developed, showing their sexual maturity in 

 spite of their small size. - An interesting point with reference to this species is 

 that 17 of the specimens (or more than 60 per cent) have an even number of 

 rays, whereas in kubiniji and mulliradiatus, the two other species with relatively 

 few rays, only 41 out of 127 (or less than 33 per cent) have an even number. 

 Now in helianthus 56 per cent have an even number of rays, and it would seem 

 as though the condition in canopus is further confirmation of the view that this 



