Description of species — cmnoidea 281 



PLATYCRINUS STELLATUS n. sp. 

 Plate 11, figures 13-14 



Description. — Calyx rather small, about as wide as high. Basal plates 

 not preserved in the type specimen. Eadial plates quadrangular, height 

 and width about equal, rather tumid below, the surface smooth, the arm 

 facets very large, subcircular, reaching to below the middle of the plates. 

 No brachial plates preserved. Ventral disk higher than the dorsal cup ; 

 above each radial are three plates arranged in arch-like manner above the 

 arm opening; on the outer surface of these plates is a disk-like plate 

 which projects out over the base of the arm, the whole combination of 

 plates having the appearance of a strong, distally flattened node-like pro- 

 jection, with the arm opening piercing the calyx in the angle between the 

 lower side of the node and the distal margin of the radial; these five 

 projections above the five radials give to the calyx a distinctly stellate 

 appearance when viewed from above. In each of the interradial areas 

 between these radial nodes of the ventral disk, and resting upon the distal 

 edges of the radials, is an interradial plate, those of four interradial 

 spaces being small and narrow, the fifth, on the posterior side, being 

 much larger. The central portion of the ventral disk is occupied by five 

 rather large, somewhat tumid or nodose plates, one being nearly central, 

 the other four being arranged around the central one on its anterior and 

 lateral sides. Posterior to the central plate of the dome, and lying be- 

 tween it and the large posterior interradial plate, is the large anal opening 

 which is directed upward. 



The dimensions of the type specimen are : Height, exclusive of the basal 

 plates, 13 millimeters; width of dorsal cup, 14 millimeters; width of 

 calyx to the ends of the radial nodes of the ventral disk, 17.5 millimeters. 



Remarks. — This species may be recognized by its strongly stellate ap- 

 pearance when viewed from above. Because of the position of the arm 

 openings beneath and even in the lower side of the prominent radial 

 nodes, the arms must have been more or less pendent when they were 

 present. 



PLATYCRINUS SPRINGE RI n. sp. 



Plate 11, figures 17-19 



Description. — Calyx small, subglobular in form, wider than high. Base 

 very shallow, saucer-shaped, the diameter of the basal disk a little more \ 

 than one-half the diameter of the calyx between the arm bases. Eadials 

 wider than high, their surface gently convex, the facet for the attachment 

 of the costal plates about one-half the total width of the plate. The first 



XXV — Bull. Geol. Soc. Am., Vol. 20, 1908 



