SHALLOW-WATER STARFISHES 277 



" Four specimens were sent to me by the U. S. National Museum. 

 Three were from Bering Island, collected by Dr. Stejneger and Mr. 

 N. Grebnitsky, in 1888. One was from Kamchatka, collected by 

 N. Grebnitsky." 



Dr. Fisher records the eight-rayed form from Bering Strait, 17 

 fathoms ; Bering Island ; and from the Pribilof Islands, in 26 

 fathoms. 



He states that he has taken seven-rayed, eight-rayed, and nine- 

 rayed young from the gonocodium of a single eight-rayed specimen ; 

 and six-rayed young from a seven-rayed specimen. This shows that 

 the number of rays is of no great importance in this species. The 

 young, when they leave the pouch, are from 12 mm. to 20 mm. in 

 diameter (teste Fisher). 



One of the eight-rayed specimens described by me was in the 

 act of giving birth to a nine- rayed young one, about 12 mm. in 

 diameter. In that specimen the interradial slits were well marked, 

 with smooth edges (not ruptured), not only where there were young 

 beneath, but also in the interradial areas where there were no young. 

 The arrangement of the paxillary spines in the interradial areas, is 

 such as to facilitate the formation of the slits. Whether there is 

 a sexual difference in this respect, I do not know. 



The species of this genus might be thought hermaphrodite, for it 

 is rather unusual to find adult specimens that do not carry young. 

 But Professor Fisher has dissected a large specimen of P. jordani 

 which proved to be a male, not differing externally from the females. 

 Probably the males are fewer in number than the females. 



Genus Ptcrasterides Verrill. 

 Type, Pteraster aporus Ludwig. 

 Pterasteridfs VEBRILL, Amer. Naturalist, XLIII, p. 547, September, 1909. 



Differs from Pteraster in being destitute of a notable central 

 dorsal oscule and in having groups of spines around the dorsal pore 

 which do not reach the supradorsal membrane. In other characters 

 much like Pteraster. Numerous young were found in the nidamental 

 cavity by Professor Ludwig. 



Professor Fisher thinks that the type was merely an abnormal 

 Pteraster militaris. Ludwig mentions young taken from the nida- 

 mental cavity, but does not say that they disagreed with the mother, 

 as would most likely have been the case if the absence of the osculum 

 was abnormal. 



