ECHINODERMS FROM GREENLAND — CLu^RK 431 



The mouth plates bear three long spines of which the two outermost 

 are subequal and the innermost, at the apex of the plate, is shorter and 

 slenderer. 



On the abactinal surface each spine bears one to four (usually two 

 or three) small crossed pedicellariae, and others occur here and there 

 on the plates between the spines. The superomarginal spines bear one 

 to nine (commonly four to six) pedicellariae in a circlet at about the 

 middle. The inferomarginal spines bear one to five (commonly three 

 or four) pedicellariae, which are more or less confined to the side 

 toward the arm tip. The spines on the actinal plates carry usually two 

 or three pedicellariae, mainly on the side away from the furrow. The 

 spines on the adambulacral plates are mostly without pedicellariae, 

 though many carry one, situated usually at or near the base. Each 

 adambulacral plate bears a straight pedicellaria situated within the 

 groove at a little distance below the base of the inner spine. These 

 pedicellariae alternate higlier and lower along the groove. 



Crossed pedicellariae are numerous abactinally and laterally. 

 Straight pedicellariae occur within the ambulacral groove, on and 

 among the adambulacral spines, in the interradial areas, and on the 

 abactinal surface of the disk w^iere they are attached to the plates. 

 They are all small. The largest are in the interradial areas and on 

 the abactinal surface of the disk where, however, they are not 

 numerous. 



The crossed pedicellariae have the proximal half of the jaw narrow 

 and the distal half abruptly expanded watli a smooth semicircular 

 distal edge, giving somewhat the impression of a horse's hoof. The 

 basal portion, approximately at right angles to the jaw, is some- 

 what longer than the latter, measuring from the constriction between 

 the two portions. 



Viewed from the interior the valves of the straight pedicellariae 

 are seen to have the sides parallel for the proximal two-thirds, thence 

 curving to an oval more or less broad tip. The sides may be 

 smooth or finely serrate, and the tip may be smooth or with the 

 center turned inward and produced into a point. 



Locality. — Between Cape Alexander and Cape Chalon, northwest- 

 ern Greenland; 25-40 fathoms; rocky bottom; Capt. Robert A. 

 Bartlett, August 2, 1937 (type, U.S.N.M. No. E.5753). 



Notes. — This species belongs to the C anntschatica section of the 

 subgenus Hexastcnas^ typified by L. {H.) camtschatica., which here- 

 tofore was known only from the coasts bordering the north Pacific 

 and the southern Bering Sea. It is not very closely related to any 

 of the north Pacific or Bering Sea species. 



It is easily distinguished from Z. polarls of the same size. The 

 abactinal spines are cylindrical, not more or less capitate as in 



