202 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



central^ large, and extended into a heavy, short spme ; the other four orals 

 proportionally small and almost flat. Eadial dome plates represented by 

 plates of a first and second order, those of the latter by two or three plates 

 to each division, alternately arranged ; all large and spine-bearing. The 

 spines near the outer margins of the disk project obliquely outward, and are 

 visible from a dorsal view of the calyx. Interambulacral plates numerous, of 

 the size of the smaller orals, and irregularly arranged. Anus excentric, at 

 the top of a large ovoid protuberance, rising conspicuously above the general 

 plane of the disk. 



Horizon and Locality. — Niagara group ; St. Paul, Shelby Co., Ind. 



Tt/pe in the collection of Wachsmuth and Springer. 



IDIOCRINUS W. and Sp. (nov. gen.). 



(t'Sto?, peculiar ; Kpivov, a lily). 



1892. W. and Sp. ; Am. Geologist, Vol. X. (September), p. 135. 



Sjn. Qazacrmus S. A. Miller (October 26, 1892) ; Adv. Sheets, 18tli Rep. Geol. Surv. Indiana, 

 p. 49. 



Infrabasals apparently five, extremely small, placed at the bottom of 

 a more or less deep concavity, and completely hidden by the column. Basals 

 fwe, very large ; the posterior one truncated b}^ the anal plate. Kadials quite 

 large ; three of them heptagonal, the two adjoining the anal side hexagonal. 

 Costals two, very short; the first quadrangular; the second pentangular, 

 the upper angle rather obtuse. Distichals two in the calyx ; short. Inter- 

 radial areas at all sides composed of a single large plate, which rises to the 

 top of the dorsal cup ; that of the anal side resting upon the basals, the four 

 others upon the sloping upper faces of the radials. Ventral disk quite vari- 

 able in form ; covered by a large, probably anchylosed oral pyramid. The 

 ambulacra tegminal ; the interambulacral spaces formed of single plates, 

 of which the posterior one is perforated by the anus, which is excentric. 

 Arms and column unknown. 



T^pe. — Idiocrinus elongatus. 



Distribution. — So far as known, restricted to the Niagara group of 

 America. 



Bemarks. — This genus differs from all other dicyclic Camerata in having 

 a single plate in the anal area, in its central, undivided oral pyramid, and in 

 having but one interambulacral plate to each side of the disk. 



