1 66 VERRILL 



which form six to eight rows; for the numerous very small dorsal 

 spines, mostly arranged in small transverse rows or combs; and for 

 the deep ambulacral grooves and long ambulacral feet. 



The adambulacral spines are crowded in three irregular rows, 

 most of them standing two on a plate, but frequently alternating with 

 one on a plate (subdiplacanthid). Those at and near the mouth 

 are very long and rather slender, terete, slightly fusiform, pointed. 

 The longest are up to 8 mm. or 9 mm. long. They decrease in 

 length distally and become more obtuse; about opposite the border 

 of the disk they are only about half as long (4 mm. to 5 mm.), or 

 about equal in length to the adjacent actinal spines, but are smaller 

 and more tapered. They all bear dense clusters of minor pedicel- 

 lariae near the ends. 



The interactinal ossicles form about five regular close rows, nearly 

 equal in size and form. The synactinal ones are only a little smaller, 

 and like the others may bear two or three spines. Many of the 

 actinal ossicles bear two spines that stand obliquely on the ossicle; 

 hence there are six to eight rows of crowded, nearly equal spines, 

 which are strong, not very long, mostly somewhat fusiform, and 

 tapered distally, obtuse or subtruncate, often slightly compressed, 

 substriate or nearly smooth, mostly slightly curved outward. They 

 bear small, dense clusters of minor pedicellariae on the outer side, or 

 sometimes small wreaths. Between all the actinal plates are regular 

 papular areas, with clusters of small papulae. Toward the base of 

 the arms, and especially on the under side of the disk, these spines 

 become longer and more acute, some of the most proximal becoming 

 twice the length of those farther out. The rows of ossicles diverge 

 somewhat at the base of the rays, and the outer ones curve upward. 

 Separated from the inferomarginals or outer ventral row by a 

 very distinct papular channel, there is a row of strong superomar- 

 ginal ossicles, each of which usually bears two or three spines, simi- 

 lar to the actinal spines in length, but smaller and rougher, with 

 sulcated tips. This row of ossicles and spines curves upward to the 

 dorsal surface at the base of the rays, and there meets the corre- 

 sponding row of the next ray. 



The dorsal spines, which are very small, nearly equal, either 

 tapered or clavate, with rough sulcated tips, are very numerous, 

 without any regular arrangement. They do not form any distinct 

 radial rows nor any very evident reticulations. Most of those on 

 the basal part of the rays stand in short transverse or oblique rows or 

 combs, varying from two or three to ten or more, but many stand 



