152 BLTLLETIN 76, UNITED STATES NATIONAL MUSEUM. 



one or two riulimentarv pedicollariffi (the spinelets being ven^ short) in each area. 

 The type has none. 



Matircporic body within its own diameter from the interradial plate, and sur- 

 rounded by about five prominent spiniferous plates. The adcentral of these is 

 the primary basal. 



Anatomkal notes. — Xo superambulacral plates; the ambulacral ossicles pro- 

 duced dorsally into a thin carina as in other species of genus (except at base of ray). 



Young. — From station 3001 are a number of young and middle-sized speci- 

 mens. These exhibit most of the characteristics of the adult, especially the club- 

 shaped inferomarginal and actinal adajnbulacral spines, pedicellarias, and minute 

 abactinal spinelets. The spine-bearing plates of disk are very prominent, but the 

 spines themselves are not so numerous nor so prominent as in the adult. The 

 thorny surface of the spines is quite apparent. Far along ray the abactinal plates 

 have only one or two minute spinelets. In such a specimen (R = 43 mm.) there is 

 a considerable area at center of disk in which no papulae occur and the actinal 

 interradial areas are relatively as large as the types. 



Type.— Cat. No. 27804, U.S.N.M. 



Type-locality. — Albatross station 37.88, off Cape Blanco, Oregon, 1,064 fathoms, 

 green mud, three specimens. 



Distrihuiion . — Southern Bering Sea to Oregon and from 987 to 1,064 fathoms, 

 green mud or ooze. 



Specimens examined. — Besides three from type-locality, thirteen from three 

 stations as follows: 3307, southern Bering Sea (lat. 53° 55' N.; long. 170° 50' W.), 

 1,033 fathoms, green ooze, two specimens; 3601, Bering Sea, midway between the 

 above and St. George Island, 1,044 fathoms, green mud, fine sand, ten specimens, 

 medium sized and small; 3607, north of Unalaska, 987 fathoms, green mud, one 

 specimen. 



Remarks. — This species can be distinguished from the two others here de- 

 scribed by the characteristic clavate inferomarginal and actinal adambulacral 

 spines of the proximal part of the ray, and by the prominent disk spines in connec- 

 tion with very delicate spinelets — several to a plate. The only species described 

 by Ludwig from the Panama-Galapagos region with which this needs comparison is 

 B. spinuliger, which differs in lacking the prominent spines of disk, in having 

 numerous (thirteen to sixteen) marginal mouth spinelets, and in lacking the 

 characteristically formed actinal spines. 



In Ludwig's kej^ to Pararchaster (restricted) this species falls in the first section, 

 next to pedicifer. It differs from this in the clavate actinal and marginal spines, as 

 well as in the following features: more prominent and more numerous abactinal 

 spines, in having three subambulacrals on proximal plates only, nineteen proximal 

 adambulacrals to ten inferomarginals, as well as in proportion and minor details of 

 armature. The two forms are not at all nearlv related. 



