600 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
CACTOCRINUS W and 85. (nov. gen.). 
(Kdxros a thorny plant, xpivov a lily.) 
Calyx generally longer than wide, the ventral disk high, conical, passing 
gradually into a strong, almost central tube. The plates of the cup orna- 
mented by radiating ridges and nodes. Basals three, comparatively short. 
Costals two, generally hexagonal and heptagonal. Distichals 1 X 10, all 
axillary. The succeeding orders of brachials, when present, also consist of a 
single row of plates, but only one plate at each side of the ray is axillary; - 
the other one is truncated, and gives off an arm which is free from the sec- 
ond or third plate; the axillary supports either two simple arms, or one from 
one side and two from the other, the arms being given off alternately from 
opposite sides like the pinnules. Arms equidistant or nearly so, long, bise- 
rial and infolding ; back and sides generally covered with nodes or thorns, 
and the pinnules with sharply pointed hooks. The pinnules are in close con- 
tact, and those of one side of the arm are placed with their ventral faces 
fronting those from the opposite side. They are composed of numerous 
elongate joints, which, with the exception of the three or four distal ones, 
are produced into sharp, prominent hooks, directed obliquely upward and 
outward, and arranged in rows parallel to the sides of the arms. The hooks 
of one pinnule curve over the back of the adjoining one, so as to give to the 
mass of pinnules, in their dorsal aspect, the appearance of a fine network 
in which their outlines cannot be distinguished. The ventral furrow is cov- 
ered by two rows of side pieces, which enclose two rows of minute covering 
plates. Interbrachials numerous, separated from the interambulacrals by the 
upper row of fixed brachials, which are in contact laterally. The plates of 
the ventral disk are more or less spinous, and so irregular in their arrange- 
ment that it is often difficult to identify the orals and radial dome plates. 
Anal tube very long and almost central. Column large; the axial canal 
pentangular. , 
Type of the genus: Oactocrinus proboscidalis (Hall). - 
Distribution. — Restricted in America to the age of the Kinderhook group 
and Lower Burlington limestone, with a single aberrant survivor in the 
Upper Burlington beds. The genus may possibly be represented in Europe 
in the Mountain limestone of Ireland ; but, so far as we know, not in Bel- 
gium, nor in the Yorkshire beds of England. 
- ee 
