104 XKW YORK STATE MUSEUM 



affords a bettor ba^iis for iiitorpietiiij: the atliiiitios of these 

 or«^ani»ins. Hoth convt^nience and necessity seem to require 

 the continued employment for the present of the term Agela- 

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

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

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

 fa^^'t that it is merely a term of convenience and not to be con- 

 founded with the strictly defined jjenus Agelacriuites. 



Lepidodiscus alleganius sp. nov. 

 PI. 10, fig. 1-5 



I>isks compressed, with gently convex upper, and somewhat 

 concave lower surface; sessile but not firmlv attached or 

 cemented. 



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

 gently sinuous near their origin for about half their lengfth; 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 ambulacral plates are 

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

 locking edges represented by a fine, serrated 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 interradiue. The imbrication 

 is in all cases directed centripetally or toward the mouth. 

 Marginal plates not noticeably larger or more prominent on this 

 surface. 



Ahoral .wrfacr. Deprf^sserl, with projecting ])eriphery com- 

 posed of more prominent ]>lates. (IcMieral surface with imbricat- 

 ing plates clearly slniwn. lier<', liowever. flie dire(»tion of flie 

 iml)rication is centrifugal ov away from tin* ciMiter of the disk 

 and is thn^ continuous in direction with IIh' imbrication of the 

 upjK*r or oral surface. 



