26 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



The mouth plates arc small and carry three spines, the innermost quite small and 

 Mt the inner furrow corner of the plate; the middle spinelet is a little longer and at the 

 inner siitun corner, but not so close to the actionostome; the third is 50 per cent 

 longer and situated at about the middle of the actinal surface of plate. All bear 

 broadly lanceolate straight pedicellariae similar to those on the furrow spines. In 

 some large examples from other localities (as station 3543) the jaws may have two 

 or three conspicuous teeth, as has the adambulacral and other straight pedicellariae. 



The papular areas are small with one to four papulae on the rays, or occasion- 

 ally slightly more. There is an intermarginal and one actinal series. (In the largest 

 specimens the papulae are more numerous.) 



Straight pedicellariae: More or less markedly unguiculate, slender, somewhat 

 hand-shaped pedicellariae occur, in forma arctica, very sparingly on the abactinal 

 surface, in the interbrachial channels, and in the intermarginal channels. (PI. 9, 

 fig. 8.) Just external to the adambulacral spines and on the oral and proximal fur- 

 row spines, there are usually a few but they are not so numerous as in forma bering- 

 ensis. Ovate-lanceolate pedicellariae are common along the furrow face of the 

 adambularcal plates. These have the tips of the jaws crossed, or one curved tip 

 meets a notched tip. In southern Bering Sea specimens (forma beringensis) the 

 unguiculate pedicellariae (pi. 9, figs. 10, 11) are sometimes fairly common abactinally, 

 but not in forma arctica. The largest are in the axils of the rays, actinally, and in 

 beringensis these may have as many as five teeth. (Station 3543, pi. 9, fig. 9.) 

 While the dimensions vary a good deal, an axillary pedicellaria of a large specimen 

 is 0.8 to 0.9 mm. long. 



Crossed pedicellariae occur in wreaths around the abactinal and marginal, and 

 as half wreaths on the actinal and adambulacral spines. In a specimen with R 36 

 mm., forma arctica, the abactinal are about 0.23 mm. long and the adambulacral 

 0.26 mm., most of the latter having a different shape from the former. (PI. 8, figs. 

 5, 5a-5h; pl. 10, figs. 1-3.) 



Madreporic body small, but variable, about 0.6 r from center of disk, and with 

 three to six spines on the adcentral margin. 



Variations. — There are at least two recognizable intergrading formae. 



Forma ARCTICA (Murdoch) 



Plate 8, Figures 5, 5a-5d; Plate 9, Figures 2, 7, 8; Plate 10, Figures 2, 2a; Plate 14, Figures 1-4; 



Plate 15, Figure 1; Plate 16, Figure 1 



The typical variety of this species, as indicated by the type series of specimens, 

 is a fairly slender rayed, small sea star with rather coarse, unequal subcapitate abac- 

 tinal spinelets, among which a very irregular radial series is discernible by reason of 

 the greater size and usually more crowded arrangement of spines. In the type 

 series the nossed pedicellariae are not very numerous on the abactinal spines, but 

 this is a character which appears to vary with every station, and there are even con- 

 aiderable individual differences at the same station. Examples from 15 to 20 fathoms, 

 Plover Bay, Siberia, and from East Cape, Siberia, are more plentifully supplied than 

 are those from the American coast, and therefore resemble forma beringensis. But 

 the crossed pedicellariae are more nearly like those of arctica, and the well-spaced 



