ACTINOCRINIDiE. 621 



Cactocrinus ornatissimus w. and Sp. 

 Plate LVII. Fig. 3. 



18S7. Mtimeriiius ornatissimus — Vf . aud Sp. ; Geol. Rep. Illinois (1890), Vol. Till., p. 163, Plate 16, 



Eg. 9 (not Plate 17, Fig. 3). 

 1890, Adinocrinus ornatissimus — S. A. Miller; N, Amer. Geol. and Pal., p. 219. 



Of medium size, specimens of light color. Dorsal cup depressed, 

 semiglobose ; height equal to half its width ; plates delicate and highly 

 ornamented, but not convex; suture lines difficult to see. The surface is 

 marked by a system of sharply elevated, very prominent rounded ridges, 

 passing from plate to plate, aud meeting in large stellate clusters in the 

 interbrachial spaces ; those following the middle of the radial series are 

 widest, and pass from the basi-radial suture into -the arms ; they increase in 

 width toward the arm bases, and divide the surface into five well defined 

 pentangular fields. Scattered between the ridges there are bead-like nodes, 

 and the ridges are more or less undulating. 



Basals short ; forming a small rim, which is slightly notched at the 

 sutures. Eadials and costals decreasing in size in ascending order, all wider 

 than long ; the first costals quadrangular with convex sides ; the second 

 generally heptangular. Distichals and palmars one, except in the outer 

 divisions of the ray,s, in which the first palmar is succeeded by two to three 

 cuneate plates, which support an arm ; while the inner ones are axillary, 

 and followed by two post-palmars with two arms ; there being normally 

 three arms to each main division, and six to the ray. Arms long, moderately 

 stout, rounded on the back, their tips cin-ved and folded inward ; they are 

 composed at their bases of cuneate pieces, which interlock and gradually 

 become biserial, every second to fourth joint of both series being long, and 

 bearing a conspicuous, tooth -like node. The intervening joints are much 

 shorter, and connected longitudinally by waving sutures. Pinnules closely 

 packed and contiguous; composed of short joints, and each one armed with 

 a short hook. Interbrachials comparatively large, occupying fully one half 

 of the whole interbrachial space, and rising to the middle of the second 

 costals ; there are two plates in the two succeeding ranges, which are fol- 

 lowed by the interambalacrals. First anal plate as wide as the radials, 

 and often higher, supporting 2, 3, and 2 plates. Interdistichals generally 

 three, with frequently a small interpalmar. Ventral disk short hemispheri- 



