Boone, Echinodermata, Cruises of "Ara" and "Alva" 169 



they fuse to a non-serrate ridge, the apex being obtuse. The collar 

 is about 2.1 millimeters long, increasing in thickness toward the 

 milled ring; both are finely striated. The third primary spines 

 are intermediate to the ambital spines. 



The secondary spines are of two kinds ; the scrobicular spines, 

 which are 3.8 to 4.2 millimeters long, flattened, tapered to rounded 

 apices, the broad outer surface frequently being transversely con- 

 cave and always finely striated longitudinally. The small spines 

 on the test and marginal ambulacral spines are only 1.8 to 2 mil- 

 limeters long, much slenderer and more pointed, and in the present 

 specimens with very large glandular ampullae. 



The pedicellariae of all three types are abundant. The smaller 

 globiferous pedicellariae average from 0.5 to 0.6 as long as the 

 large globiferous pedicellariae, which very much resemble poppy 

 buds in outline. The majorit>^ of the small globiferous pedicel- 

 lariae have the distal third of the inner face of the valve occupied 

 by a narrow cavity, subtriangular in outline, although even on 

 the same specimen there is considerable individual variation 

 existent. 



The tridentate pedicellariae average 1.5 times the length of 

 the large globiferous pedicellariae, but are quite slender with the 

 dilated proximal cavity of each valve divided by a median cavity; 

 the lateral margins of the distal three-fourths being finely ser- 

 rate, converging to an acuminate apex. 



The present series of specimens yield the following measure- 

 ments, expressed in millimeters : 



Primary Spines : 



