372 BULLETIN 70, UNITED STATES NATIONAL MUSEUM. 



two scries united by a continuous membrane; suboral spine as slender or slenderer 

 than innermost oral and usually slightly shorter. 



Notes on Pacific specimens. — Most of the specimens are very large, the spines 

 being heavy and the integumentary developments of the actinal surface thick and 

 tough. In the specimen from off San Diego the spines are more delicate and the 

 whole animal more lax. 



The specimens agree very well with Atlantic examples, with which comparison 

 has been made. Judging by the single Californian example from station 4353, and 

 one Japanese specimen, 475 fathoms, Suruga Gulf, variation has been toward a slight 

 decrease in the number of spines in the former, especially on the nonjirominent 

 adambulacral plates, and a slight increase in the latter (seven spines in the promi- 

 nent combs, six in the nonprominent). In the Japanese example there are about 

 nine spines to the paxilhp, which have very long pedicels relatively slightly longer 

 than in Atlantic examples. 



^AJl the specimens are bristling with the stout central paxillar spines which push 

 up the membrane and occasionally protrude through. In small examples the 

 spiracles are disposed in seven regular series radiating from the central spine, but 

 later the arrangement becomes irregular (except in the Japanese specimen where 

 the series are fairly straight). 



The "prominent" adambulacral combs usually have the innermost, or furrow, 

 spine long, while the "nonprominent" plate has a very small furrow spine, though 

 sometimes it is long. Always, however, the comb is set back. The nonprominent 

 plate may have as many spines as the prominent, though in that case the furrow 

 spine is usually small; there is ordinarily one spine less on the nonprominent plate. 

 In a large specimen, beginning with a prominent plate at base of furrow, the number 

 of spines run as follows, the nonprominent being marked by a star: 5, 5*, 6, 4*, 5, 4*, 

 5, 4*, 4, 4*, 5, 4*, 5, 4*, 4, etc. The innermost spine, if fully developed, is the longest, 

 the rest decreasing slightly in length, outward. Sometimes the second is the longest, 

 or all are very nearly the same length, or at base of ray the spines are graduated 

 in length from the innermost outward. The saccular prolongations of the web at 

 tip of spines vary in length, being usually nearly as long as the spine itself. In small 

 specimens, however, they are not prominent. The first ambulacral web is continued 

 across to meet its fellow, just back of the mouth plates. 



The actinolateral membrane is thick and fleshy in the large examples, in some of 

 which the free border forms a nearly straight edge to the side of the body, but is 

 arched inward in others. Small specimens have the membrane thinner, so that the 

 spines show through. The ambulacral webs are continued out upon the membrane 

 for a short and variable distance, farthest, apparently, in the ver}' old specimens. 



The madreporic body is large, very convex, marked by coarse radiating furrows. 

 There is no tuft of spinelets from the summit as in Pteraster tesselatus. 



One of the specimens has six rays, but is otherwise like the rest. 



Type-locality. — Drobak, Norway; 60 fathoms. 



Distribution. — Probably circumpolar; known from the north Atlantic, on the 

 west side, from 35° to 45° north latitude (Verrill) and on the east side from Norway 

 and Barents Sea; in the north Pacific, from San Diego, California, and Suruga Gulf, 

 Japan, north to Bering Sea. Vertical distribution: in the Atlantic 50 to about 580 

 fathoms; in the Pacific, 81 to 640 fathoms. 



