568 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



convex longitudinally, one fourth amaller 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, wliich 

 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. mulliramosus, 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 2, 3, 5, and 

 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. 



Bemarlcs. — 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 Griflathi W. and Sp. (nov. spec). 



Plafe LII. 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 



