498 THE CKINOIDEA CAMERATA OF NOKTH AMERICA. 



which generally has but two arms, there are 3X2 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 i^^ 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. Eays 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. 



TiJiKS in the Illinois State collection, Springfield. 



Remarks. — Differing from all preceding species in the greater number 

 of arms, and in the form and proportions of the calyx. 



Agaricocrinus nodulosus, var. Macadamsi (Woethen). 

 Plate XXXIX. Fig. 6. 



1891. Agaricocnnus Macadamsi "Woethen ; Geol. Rep. Illiuois, Vol. VIII., p. 94, Plate 13, 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. 



