472 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
times as wide. Interbrachials three; the first very large, as wide as high, 
the two upper quite small. They are followed by two still smaller pieces, 
which are on a level with the arm bases, and these by equally small inter- 
ambulacral plates ; there being no interdistichals in the dorsal cup, but several 
in the tegmen between the ambulacra. First anal plate much longer than 
the radials, and the largest plate of the dorsal cup. It is followed by three 
or four higher anals, longitudinally arranged, which decrease rapidly in size 
upward, each one having an interbrachial at the sides. There are numerous 
plates above, which form a longitudinal ridge with a deep sulcus at each 
side. ‘The anus, which is placed at the upper end of this ridge, opens out 
laterally. Orals a little more convex than any of the other plates of the 
tegmen ; the posterior one very large, its size equal to that of two of the 
others, and generally extended into a short spine. Food grooves covered by 
a few alternately arranged medium-sized plates, which are more prominent 
than the interambulacrals, especially on approaching the arms. Column com- 
paratively short, gradually tapering, and terminating as a fine thread; its 
whole length being from 7 to 9 cm. The joints throughout are moderately 
long, and increase in length downward. They are in the upper part of the 
stem distinctly rounded at their margins, and project conspicuously over the 
younger joints; but at the lower part cylindrical and of equal width, giving 
off toward the end at irregular intervals, and at different sides, rather stout 
and long cirri. 
_ Horizon and Locality.— Kinderhook group; Le Grand, Marshall Co., 
Iowa. 
Types in the collection of Wachsmuth and Springer. 
Aorocrinus radiatus W. and Sp. 
Plate XLV. Fig. 1. 
1890. Doryerinus radiatus— W. and Sr.; Geol. Rep. Illinois, Vol. VIII., p. 176, Plate 17, Figs. 5, 5a. 
1890. Dorycrinus radiatus 8. A. Mituer; N. Amer. Geol. and Paleont., p. 240. 
Resembling the preceding species, but having a different arm formula, and 
radiating ridges upon the plates. From the radials two low, rounded ridges 
pass out to the basals, two to adjoining radials and the first anal plate, and 
one to the first interbrachials. The latter plates have nine ridges, two meet- 
ing with those from the radials, the others, which are somewhat smaller, with 
the costals and the interbrachials of the second range. The ridges are well 
