ie Se ne 
602 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
than long. First costals larger than the second, quadrangular or pentangular; 
the second pentangular or heptangular. Distichals one, axillary, supporting | 
within the calyx two single palmars, followed by the free arm plates, which | 
from the second piece are arranged in double rows. Arms crowded, long and 
heavy ; their upper ends rapidly tapering to a fine point; the plates some- j 
what transversely angular, and the suture lines parallel. Pinnules in close 
contact, composed of about fifteen joints, from two and a half to three times 
as long as wide ; all, with the exception of the three upper ones, provided 
with a prominent, sharp hook, directed obliquely upward, and arranged 
longitudinally in rows parallel with the sides of the arms. Regular inter- 
brachials: 1, 2,1; large specimens have an additional row of two plates, 
and the second palmars take part in the calyx; the palmars of adjacent 
rays in contact laterally. The first anal plate is followed by three to five 
interbrachials, there being no higher anals, and the species has no interdis- 
tichals. Ventral disk conical, composed of rather large, spinous or nodose 
plates, separated by small, convex pieces. The plates are irregularly 
arranged, and the orals and radial dome plates are with difficulty recog- 
tube, which extends considerably beyond the limits of the arms, is composed 
nized ; the posterior oral is erect, and forms a part of the anal tube. The | 
of convex pieces; it tapers gradually, and is quite slender at the upper | 
end. Column strong, composed near the calyx of alternate thick and thin 
joints with rounded edges; the former increase in diameter downwards, r 
while the latter grow narrower, gradually become cylindrical, and increase | 
in number quite rapidly, there being already seven to the internode at 
90 mm. from the calyx. 
florizon and Locality.—One of the characteristic fossils of the Lower 
Burlmgton limestone; Burlington, Iowa, Sedalia, Mo., and Lake Valley, 
New Mexico. 
fiemarks. —We regard Hall’s Actinoerinus quaternarius and its variety 
spimferus, his A. excerptus, A. themis, and A. lagena, as mere variations of this 
species, differing slightly in the matter of ornamentation. They cannot be 
separated in large collections, although they may seem to be quite distinct 
in individual specimens. Our study of the species is based upon over one 
hundred good specimens. 
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