94 BULLETIN 16, UNITED STATES NATIONAL MUSEUM. 



0.18; wliilc a fifth series does not extend beyond the third inferoraarginal. (Com- 

 pare with table under erimius.) Between first inferoraarginal and third adambu- 

 lacral are seven plates. The series meeting the first and second adambulacrals do 

 not reach the marginals. Intermediate plates bear a marked tabulum or carination 

 crowned with a very compact group of numerous (about fifteen to twenty) round- 

 tipped, flattened, scale-like spinelets directed toward marginal plat«s; surrounding 

 this elliptical or ovoid group of imbricating spinelets is a peripheral series of about 

 fifteen to twenty-five slightly curved, round-tipped, slender, flattened spinelets 

 resembling flower petals. Indeed, the whole group greatly resembles an asymmet- 

 rical miniature chrysanthemum blossom. The central spinelets are much less 

 mimerous in eximius and never of the flattened imbricating squamiform shape. 

 The furrows running interradially between the actinal paxillae are narrower in 

 the present species than in the foregoing. 



Madreporic body very large (13 mm. in diameter) with fine centrifugal stria- 

 tions. It is subcircular, with a scalloped edge, and its center is about midway 

 between inner edge of superomarginals and center of disk. The surface is uneven, 

 and is entirely obscured by about thirty to thirty-five very large paxillte. One 

 of these exceeds the rest in size. 



Anatomical notes. — The internal anatomy does not difter in any very impor- 

 tant respects from that of D. eximius: superambulacral plates the same, as also 

 the details of the water vascular sj'stem. The intestinal coecum is the same shape, 

 but lies in the left bivial interradius (very nearly the position in eximius); anus 

 present, of conspicuous size; connections as in eximius. Gonads arranged as La 

 eximius, but in specimen examined they extend farther along the ray, beyond 

 middle. 



Variations. — The variations exliibited by the few available specimens are 

 slight and concern chiefly minor details of ornamentation already mentioned. 

 One specimen from station .'^.331 has the rays a trifle shorter and broader at the 

 base than the rest. Despite small differences in spine counts, the type facies is 

 maintained by all the specimens, and one can distinguish them at a glance from 

 eximius. 



Type.— C&t. No. 24341, U.S.N.M. 



Type locality. — Albatross station 3331, north of Unalaska, 350 fathoms, mud 

 (four specimens). 



Distribution. — Bering Sea and south of the Aleutian Islands, 121 to 3.51 

 fathoms. 



Specimens examined. — Seven specimens, besides four from type locality, one 

 from station 3330, same locality, 351 fathoms, black sand, mud; two from station 

 3337, south of Unimak Island, 280 fathoms, green mud; one from station 3489, 

 west of Pribilof Islands, Bering Sea, 184 fathoms, green mud; one from station 

 3500, south of the Pribilof Islands, 121 fathoms, fine gray sand. 



Remarl-s.— As detailed in the foregoing description, this species differs from 

 Dipsacaster eximius in the shape of rays in large specimens, in having smaller 

 paxilhr, which have fewer spinelets, and these not descending far down the pedicel; 

 in not having the paxillw conspicuously enlarged on center of disk and along middle 

 of ray; in the shape and position of median radial plates and in number of papulje 



