REPORT ON THE ECHINOIDEA MORTENSEN 



279 



with some lateral serrations which are not very conspicuous; they 

 are straight or at most very slightly curved. The fourth is transi- 

 tional to the ambital spines. 



The scrobicular spines are about 2 mm. long, smooth, thin, and 

 flat, or with a slight indication of being excavated toward the end, 

 which is straight cut; the sides are very nearly parallel. The mar- 

 ginal ambulacral spines are of the same general shape, but more 

 narrow and more slender; they may be slightly widened toward the 

 point; those near the peristome are scarcely different from the 

 ambital, as is the case in some goniocidarids. The miliary spines 

 are slender, conical, with finely serrate ridges. 



Fig. 16.— Details of hair-covering of primary spines of Schizocidaris 

 serrata mortensen. a. part of spinule with the fenestrated outer 

 layer formed by the hairs; two columns are seen to connect the 

 outer layer with the compact mass of the spinule. ft. part of the outer 

 layer, half in profile, showing three supporting columns. c. part of 

 the outer layer, seen from the inside. x120 



Only the small globiferous form of pedicellariae is found, and these 

 are not very numerous or very conspicuous, scarcely exceeding a size 

 of 0.2 mm. in length of head, while the stalk may be as much as 

 0.6-0.7 mm. The valves (pi. 78, fig. 1) are of the usual goniocidarid 

 type, with a conspicuous end tooth; the opening is rather unusually 

 short; the form with the long, narrow slitlike opening so character- 

 istic of S. assimilis has not been found in this species. 



The spicules of tube feet are very numerous, slender, and more 

 spiny than in S. assimilis. 



In color the primary spines are white (when clean), the test and 

 secondaries yellowish white. The apical system is greenish, the green 

 color being in the main confined to the genital plates and to the inner 

 27566—27 4 



