068 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
convex longitudinally, one fourth smaller than the costals, and-as wide as 
long. They support at their outer sides an arm, which from the second or 
third plate is free and biserial ; and from the inner side three palmars, which 
give off two arms. There are six arms to each ray from the calyx, but 
these generally branch once again in their free state, rarely twice. Arms not 
quite as long and stout as in A. multiramosus, and more rapidly tapering; the 
pinnules stronger. The latter are composed of eight or nine very long joints, 
of which only the two proximal ones have hook-like processes. Regular 
interbrachials: 1, 2, 3, 4, 3 — sometimes three in the second row — the first 
larger than the costals, the succeeding ones decreasing in size upwards. 
Anal plate a little smaller than the radials, and followed by, 23. os cama 
numerous other irregular plates. The form of the ventral disk cannot be 
ascertained, both type specimens being flattened, but it was probably de- 
pressed conical. The plates are rather large, strongly convex, rounded at 
the top, and nearly uniform in size. Nothing is known of the anal tube. 
Column very large near the calyx. 
Horizon and Locality. — Keokuk group; Indian creek, Montgomery 
Co., Ind. 
Types in the collection of Wachsmuth and Springer. 
Lemarks. — This species differs from the preceding one, and all others of 
the Keokuk group, in the thinness of its plates, and in having the ridges 
upon the surface produced by folds in the plates. The second costals are 
much larger, and while in the other species the brachial extensions begin 
above or below the second costals, they commence in this at the top of the 
distichals. | 
Actinocrinus Griffithi W. and Sr. (nov. spec.). 
Plate LIT. Fig. 7. 
Of medium size. Calyx higher than wide, the brachial extensions nar- 
row; interspaces wide. Dorsal cup three times as high as the ventral disk, 
decidedly swelling across the middle of the radials and anal plate, where the 
section is distinctly angular, and wider than at the top of the first costals. 
Plates rather delicate, covered with ridges, which meet at the middle of the 
plates within a small node. There are four such ridges between the radials 
and basals, of which the two middle ones are the most conspicuous ; one or 
two form a continuous ring around the radials and anal plate, while there is 
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