498 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
which generally has but two arms, there are 3 X 2 distichals; while in the 
rays with three or four arms, the second distichal is axillary in one or both 
divisions, and is followed by two rows of palmars. Arms 4;%, exceptionally 
three in the anterior ray, which are free above the second palmar, or third 
distichal respectively, and they are heavy, long, and tapering. Pinnules 
stout, composed of joints which are nearly three times as long as wide. First 
interbrachial narrow and long, rising to the middle of the first distichals; the 
two plates of the second range as long as the first, but only half as wide. First 
anal longer than the radials, and longer than wide; the second anal elongate, 
widest at the upper end, the interbrachials at the sides widest in the middle, ' 
all curving from within the lower concavity abruptly upward. Anus in the 
middle of an oval shaped protuberance, opening obliquely outward. Orals 
in contact laterally ; all convex, the posterior one a little the largest. The 
ambulacra are represented not only by the usual number of radial dome 
plates, but by additional plates, either placed in one or two series. Rays with 
three arms have a single large secondary radial dome plate at one side, but 
those with four arms have one at each side. The interambulacral spaces are 
somewhat depressed, and are occupied by a few small, irregular plates. 
Horizon and Locality. — Keokuk group; Keokuk, Iowa, Jersey Co., Ills., 
Montgomery Co., Ind., White’s creek, Tenn., and Canton, Ind. 
Types in the Ilinois State collection, Springfield. 
ftemarks. — Differing from all preceding species in the greater number 
of arms, and in the form and proportions of the calyx. 
Agaricocrinus nodulosus, var. Macadamsi (Worruen), 
Plate XX XIX. Fig. 6. 
1891. <Agaricocrinus Macadamsi WortuEN ; Geol. Rep. Illinois, Vol. VIIL, p. 94, Plate 18, Figs. 2, 2a. 
The specimen for which Worthen proposed the above name, agrees in 
the most essential points so closely with A. nodulosus, that we think it is only 
a variety. Yet there are some differences; the specimens as a rule are 
larger, and differ considerably in the form of the calyx, which is high-hemi- 
spherical, as opposed to depressed subpyramidal in the other. The sides of 
the ventral disk are inflated below, the top being almost flat, and the orals 
are larger and but very slightly convex. In the structure of the dorsal 
cup the two forms are almost identical, and they have the same number of 
arms. 
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