286 bulletin: museum of compaeative zoology. 



personatus Sladen, 1891. Proc. Roy. Irish Acad., (3) 1, p. 694. Atlantic Ocean, 



off Irish coast, 750 fathoms, 

 ingoufi Perrier, 1891. Ech. Cap Horn, p. K 144. Antarctic Ocean, near Cape 



Horn, 150 fathoms, 

 lebruni Perrier, 1891. Ech. Cap Horn, p. K 145. Antarctic Ocean, near Cape 



Horn and further south, 45-250 fathoms, 

 alveolatus Perrier, 1894. Tal. et Trav. Ech. : Stell, p. 183. Atlautic Ocean, 



near Azores, 2256 fathoms, 

 sordidus Perrier, 1894. Tal. et Trav. Ech. : Stell., p. 1S2. Atlantic Ocean, off 



Morocco, 633 fathoms, 

 multispinus Clark, 1901. Proc. Bost. Soc Nat. Hist., 29, p. 326. Puget Sound, 

 jordani Fisher, 1905. Bull. Bur. Fish., 24, p. 314. Eastern Pacific Ocean, off 



San Diego, Cal., 642-650 fathoms, 

 reticulatus Fisher, 1906. Starfishes Haw. Isl., p. 1098. Pacific Ocean, near 



Hawaiian Islands, 284-298 fathoms, 

 obesus Clark, supra, 

 multiporus Clark, supra. 



Key to the species of Pteraster. 



Form more or less stellate, R > 1.8 r, usually 2-3.5 r. 



A stout spine (superoral) present on surface of each oral plate. 

 A more or less conspicuous opening (osculum) present in centre of abactinal 

 surface. 

 Adambulacral comb with more than 5 spines. 

 Stalk of paxilla short, not much higher than thick ; oral spines 6, similar, 



none so large as superoral militaris. 



Stalk of paxilla high and slender ; oral spines 5, innermost much the larg- 

 est, larger than superoral caribbaeus. 



Adambulacral comb with 3-5 spines. 



Oral spines 6; supradorsal membrane thick and smooth . . . lebruni. 

 Oral spines 4; supradorsal membrane thin. 



Paxillae with numerous (5-10) spinelets; superoral spine shorter and 

 stouter than innermost oral ; 4 well-developed adambulacral spines 



ajffims. 



Paxillae with few (1-3) spinelets, of which one is very long ; superoral 



spine long, equalling innermost oral ; innermost of 4 adambulacral 



spines very small or wanting jordani. 



No osculum present aporus. 



No superoral spine present. 



Adambulacral spines 5, in curved series ; oral spines 5 . . . . personatus. 

 Adambulacral spines 4, in straight series ; oral spines 6 . . . . sordidus. 

 Form more or less pentagonal, R < 1.8 r, usually 1.3-1.7 r ; superoral spine present. 

 Adambulacral armature of 6-7 spines ; paxillae spinelets 8-15. 



Abactinal surface more or less swollen and rougli or warty in adult; oral 

 spines 6 (5-7). 



