142 NATURAL HISTORY BULLETIN 



The interactinal plates form one row of four or six, and four 

 rudimentary plates of a second row. 



Pectinate pedicellariae, nearly circular in form, exist between 

 most of the plates of the first row and rudimentary ones between 

 those of the second row, so that there are three, four, or more on 

 each area. 



The four apical or peroral spines are much stouter than the 

 adorals and blunt, the two central ones most so, but not long. 

 Each row of adoral or lateral spines has about nine slender, 

 closely packed, subequal, and not very long spines. There are 

 ten to twelve crowded, small epioral spines on each jaw-plate, 

 the adoral one larger. 



Younger specimens, with the greater radius 12 to 13"^, have 

 the same form and many of the special characters are developed. 

 They have 12 marginal plates, obliquely placed. There is but 

 one papular pore on each radial area. That is median and rep- 

 resents the larger median pore of the type. It is surrounded 

 by four polygonal plates. When the dorsal plates are denuded 

 of spines they appear closely united in a mosaic; they are of 

 unequal sizes, larger than in most species, only slightly convex, 

 and distinctly polygonal. On the disk and bases of the rays 

 they are larger and many are regularly hexagonal. They retain 

 the polygonal form nearly to the tips of the rays. 



Adambulacral plates have six to eight very slender furrow- 

 spines and part have two slender spines on the actinal side. 

 There are only four interactinal plates, and only one rudimen- 

 tary pectinate pedicellaria, in some; while in other young of 

 similar size there are two pedicellariae to each area. 



According to Perrier's description in 1894 (p. 276) of what he 

 then called C. mirabilis the specimens (mostly very young) had 

 the following characters: 



The larger radius does not exceed 30°"°^. The superomarginal 

 plates are twenty-two; they stand obliquely and alternate with 

 the lower ones and extend somewhat onto the upper surface; 

 their outline, seen from above, is a parallelogram with inclined 

 sides; they are covered with small spinules and have one pretty 

 long marginal spine on each plate. 



The inferomarginals are a little longer than wide; they are 

 covered with small spines and have one long acute marginal 



