1 
792 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
radials, their sloping upper faces supporting from 1 to 3 X 4 fixed palmars, 
of which the proximal ones touch with their outer faces the radials, There 
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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 | | 
a considerably smaller than the radials. The plate generally rises to the 
SSO 
height of the radials and sometimes beyond them, but occasionally is shorter, 
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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 beyond 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 subtegminal. Column round; 
axial canal small. 
* In one specimen we observed a small triangular piece above the regular anal plate, which we regard 
as tcidental, and not of structural value, 
