470 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
enclose a large interdistichal. Column composed of large and small joints, 
the larger or nodal joints increasing in width downward, and at 4 cm. from 
the calyx are twice as wide as the intervening pieces; they are also much 
longer and angular at their outer edges. 
Horizon and Locality. — Lower Burlington limestone; Burlington, Iowa, 
Sedalia, Mo., and Lake Valley, New Mexico. This is one of the most char- 
acteristic species of the lower Burlington division. 
fiemarks. — Actinocrinus tricornis and A. pendens, both described by Hall, 
are undoubtedly specifically identical with Dorycrinus unicornis. In the first 
the posterior radial dome plates are extended into spines ; in the second the 
nodes of the radials and first anal plate are “ elongate and subclavate, being 
contracted in the middle, and swelling out at the extremities.’ Among this 
variety also we find specimens with one, two, or three spines upon the ven- 
tral disk, which are comparatively longer in young specimens. In the speci- 
mens from Pike Co., Mo., described by Rowley and Hare as Dorycrinus 
inflatus, the plates of the dorsal cup are less angular than usual’ in this 
genus. 
AOROCRINUS W. and Sp. (nov. gen.). 
(“Awpos immature, xpivor a lily.) 
The species small. Form of the calyx and arrangement of the plates 
similar to Dorycrinus. As in that genus, the arms are arranged in groups, 
and vary in number among the rays, the anterior ray generally having 
the fewest. The arms are stout and packed closely together, there being 
invariably but one arm from each ambulacral opening in the calyx. The 
ventral disk, as a rule, is shorter than the dorsal cup, the plates are smooth 
or slightly convex, except the posterior oral, which is more or less elevated 
and frequently tuberculiform, but not actually spinous. The ambulacra are 
tegminal, and covered with two rows of small pieces. The anal area is com- 
posed of small plates, generally forming a protuberance or low ridge, which 
slopes downward almost in a straight line from the edges of the posterior 
oral to the first anal plate. The anus is placed near the upper end, and 
faces laterally. 
Distribution. — This genus occurs in America in the Hamilton, Kinder- 
hook, and in both divisions of the Burlington group. It survived to the 
Keokuk group, where it is represented by only a single species. In Europe 
it is possibly represented by “ Actinocrinus” prumiensis Miiller, from the De- 
j 
* 
F 
