184 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



/?f marts.— This species is variable in the Athintic, and the Pacific specimens 

 are certainly no exception to the rule. Greater diflercnces are observable between 

 specimens from station 3258 than between an example from off Newport, Rhode 

 Island, and two from Norway, and a slightly larger one from 3257, near Unimak, 

 Aleutian Islands. The specimens from Kadiak Island and Shehkof Strait are frankly 

 not tyi)ical, but appear to be intergrades with alascensis. Japanese specimens 

 are variable and not quite typical. The specimens from Matsushima, in proportion 

 to length of ray, have fewer and hence longer marginals, which are wide. All the 

 granulation is low, coarse, and very compact, and the adambulacral spinelets are very 

 heavy in proportion to length, those on outer half of plate being granuliform. The 

 wide marginals are dupHcated in an Alaskan specimen from station 3258, there 

 being also a more typical specimen from the same dredge haul. The enlarged 

 actinal intermediate spinelets on both Alaskan and Japanese specimens (of which I 

 have examined a number) are quite variable, sometimes being absent, while equal- 

 sized examples have them. Postadambulacral fascioles are not always evident. 



It appears as if tliis species, spreading south along the Alaskan coast, had 

 changed into a form with narrower superomarginals, having less granuliform arma- 

 ture on the actinal surface, and less compactly placed granules on the abactinals. 

 Along the Asiatic side the development has been toward fewer and broader supero- 

 marginals, with more compact abactinal granules, and an accentuation of the 

 granuliform character of the actinal armature. The Japanese form has departed 

 less from the type than has the British Columbian. 



This species is the north Pacific and Atlantic representative of Ps. discus Sladen 

 (from Messier Channel, between Chile and Wellington Island), to wliich it is closely 

 related. It may be that Ps. -pulcher Ludwig (Galapagos to southwest of Acapulco), 

 founded on very small specimens, is the connecting link between the two forms. 



A few words concerning the name adopted may be in order. In the Museum 

 of Comparative Zoology are three specimens of " Astropecten parelii" from Norway, 

 presented by Professor Sars in 1852. These agree very well with the original 

 description and figures of Diiben and Koren. There are no differences of importance 

 between these specimens and an example of Pseudarchastcr intermedius from off 

 Rhode Island. Similarly, the Norwegian specimens belong to the same species as 

 the Alaskan. There is far more difference among the various Alaskan examples 

 than exists between these on the one hand and either the Norwegian or Rhode 

 Island specimens on the other. The width of the paxiHar area on the arm varies 

 in tliis species, even in specimens from the same locaHty. It is not surprising, 

 therefore, that the area is narrower in the specimens from Norway, just mentioned, 

 than in the figure of Diiben and Koren." Diiben and Koren figure also the supero- 

 marginal plates and paxillse, the inferomarginals and adambulacral plates, and 

 fortunately the tube feet. These have strong sucking disks. The figure is enough 

 to place the animal in Pseudarcliaster. 



That Astropecten parelii and Pseudarcliaster intermedius are one and the same 

 (somewhat variable) species I have not the slightest doubt. I also doubt if Pseud- 

 arcliaster faUax is anything more than a variety. 



" Plate 7, fig. 14. 



