792 THE CEINOIDEA CAJIERATA OF KOETH AMERICA. 



radials, their sloping upper faces supporting from 1 to 3 X 4 fixed palinars, 

 of which the proximal ones touch with their outer faces the radials. There 

 are no interradials nor interaxillaries within the dorsal cup, and, as a rule, 

 there is but one anal plate,* which is elongate-subtriangular, and always 

 considerably smaller than the radials. The plate generally rises to the 

 height of the radials and sometimes beyond them, but occasionally is shorter, 

 and the two posterior radials meet over its apex. Arms twenty, short, bise- 

 rial, simple, arranged in groups of four, separated by the appendages, so as 

 to divide the arms of the same ray among two compartments. Pinnules 

 short ; in close contact. Tegmen highly elevated, pyramidal, pentagonal in 

 outline ; the sides of the pyramid interradially disposed, and longitudinally 

 depressed so as to form niches for the reception of the arms ; the angles are 

 excavated or pierced, and support the large radial processes, which do not 

 necessarily pierce the test. Four of the interradial spaces are of similar size, 

 and composed of three to six oblong plates; the posterior one is widest, and 

 its plates are most numerous. The first interambulacral rests upon the 

 sloping outer ends of two adjoining palmars, and between two secondary 

 radial dome plates ; it is followed by others, which are distributed around 

 the bases of the wing-like appendages. The anus is almost central, and 

 surrounded by a large number of minute pieces, which form a little cone, 

 or, more frequently, a sort of mammiform protuberance. Orals large, resting 

 directly upon the interambulacrals ; the posterior one wedged in between 

 the other four. 



The wing-like appendages, which probably represent the first radial dome 

 plates, form the most characteristic feature of this genus. Their form is very 

 variable, being in some species spatulate, in others claviform or cuneiform ; 

 in some thin and knife-like, in others thick and rounded, while they bifurcate 

 in still others. The plates rise to the full height of the disk, and extend later- 

 ally far beyond it and bej^ond the arms ; they generally rest upon the surface 

 of the disk, within pits or grooves formed by the bevelled or inclined lateral 

 edges of the interradial and oral plates. Beneath them there are over each 

 ray two smaller radial dome plates of a second order, which rest against the 

 plates of the dorsal cup, and enclose a large interambulacral plate. The 

 upper edges of the latter plate are excavated, and form the lower ends of 

 the sockets for the appendages. Ambulacra sub tegminal. Column round; 

 axial canal small. 



* 111 one specimen Tve observed a small triangular piece above tlie regular anal plate, ■n-liicli "we regard 

 as iuoideutal, and not of structural value. 



