194 NEW YORK STATE MUSEUM 



affords a better basis for interpreting the affinities of these 

 organisms. Both convenience and necessity seem to require 

 the continued employment for the present of the term Agela- 

 crinites in a broad sense for such species as have not been 

 or can not yet be subjected to close analysis, but in such a case 

 the name should, I believe, be used with full admission of the 

 fact that it is merely a term of convenience and not to be con- 

 founded with the strictly denned genus Agelacrinites. 



Lepidodiscus alleganius sp, nov. 

 PI, 10, fig. 1-5 



Disks compressed, with gently convex upper, and somewhat 

 concave lower surface; sessile but not firmly attached or 

 cemented. 



Oral surface. Kays five, all contrasolar ; very narrow, direct or 

 gently sinuous near their origin for about half their length ; then 

 bending more or less abruptly, the extremital part running close 

 within or subparallel to the margin and varying in its curvature, 

 assuming the aspect of a whiplash. Oral aperture elongate, and 

 from each extremity arise two of the rays, the fifth departing 

 from the middle of the upper edge and lying opposite the anal 

 pyramid. In all observed specimens the ambulacra! plates are 

 concealed by the rows of cover plates with their convex inter- 

 locking edges represented by a fine, serrated 1 median line on 

 all rays; this line also extends over the oral area. Anal pyramid 

 circular, composed of 10 triangular plates. 



Thecal plates on interradii imbricating, with no difference 

 apparent in the plating of the anal interradius. The imbrication 

 is in all cases directed centripetally or toward the mouth. 

 Marginal plates not noticeably larger or more prominent on this 

 surface. 



Aboral surface. Depressed, with projecting periphery com- 

 posed of more prominent plates. General surface with imbricat- 

 ing plates clearly shown. Here, however, the direction of the 

 imbrication is centrifugal or away from the center of the disk 

 and is thus continuous in direction with the imbrication of the 

 upper or oral surface. 



