120 CLARK : NEW GENERA OF ECHINODERMS 



in the concavity of each of the crescentic abactinal plates, except in 

 the mid-dorsal line, where some plates may be without them, and at the 

 end of the arms, where they occur in a single line on either side of the 

 median line, and a quadruple, later triple and double, line just above 

 the superomarginals. The tip of the arm is entirely without papulae. 

 On the disk papulae occur one to a plate in a more or less triangular 

 area within each arm base; scattered papulae occur in the center of 

 the disk. 



In the proximal three-fourths of the arm the superomarginals cor- 

 respond with the inferomarginals, and are of about the same size; 

 in the distal fourth of the arm they become irregular in position and 

 indistinguishable from the abactinal plates; at first they are narrow 

 and transversely oblong, becoming triangular after the fourteenth. 

 Their armature is the same as that of the abactinal plates, from which 

 they are distinguishable only by their shape. 



The inferomarginals, 111 in number, are at first longitudinally oblong, 

 becoming squarish at the middle of the arm, and transversely oblong 

 distally; their armature resembles that of the superomarginals. 



The actinal intermediate areas are narrow; the plates are arranged 

 in rows parallel to the furrows; one row reaches to the distal fourth 

 of the arm, or possibly beyond; a second reaches the 25th inferomarginal ; 

 the third reaches the twelfth inferomarginal ; the fourth extends to the 

 seventh superomarginal ; and the fifth to the fifth; beyond the fifth 

 row there are a few additional plates. The armature consists of from 

 7 to 16 (usually about 12) well spaced sacculate spines with fluted and 

 spinous sides, ending in a tuft of spinelets. On the arms the spines on 

 the actinal intermediate plates resemble those on the abactinal plates 

 rather than those on the interradial regions of the disk (just described), 

 but are larger and longer. 



The armature of the adambulacral plates consists of four or five 

 long furrow spines, the inner very slightly the longer, set in a slightly 

 curved comb ; beyond these there is a row of four or five spines resem- 

 bling those on the actinal intermediate plates, but somewhat longer and 

 stouter; this row is rather more strongly curved than the furrow series 

 and is placed diagonally, so that the proximal end is farther from the 

 groove than the distal ; this obliquity decreases distally and is not notice- 

 able in the outer two thirds or half of the arm; beyond this second row 

 there are a few additional shorter spines, not distinguishable from those 

 on the adjacent actinal intermediate plates. 



The mouth plates are small, bearing on the furrow margin five 

 long flattened spines decreasing in length and stoutness outwardly; 

 these spines are finely fluted, with saw teeth on the ridges; within this 

 furrow series is a second series of five similar but shorter spines; the 

 remainder of the surface of the mouth plates bears four or five spaced 

 spines similar to those on the actinal intermediate plates. 



Color in alcohol dark reddish brown. 



Type.— Cat. No. 36899, U. S. N. M., from "Albatross" Station 

 3746, Sagami Bay, Japan, in 49 fathoms. 



