Fauna of the Morrow Group 
103 
five, closely united by scarcely discernible sutures into a large 
convex pentagonal plate ; the posterior and right posterio-lateral 
basals hexagonal, the others pentagonal, each nearly as large 
as the combined infrabasal plates and extending outward and 
upward beyond the plane of greatest diameter of the cup, thus 
including its most convex portion; radials pentagonal, their 
height about three-fifths their width, very gently convex longi- 
tudinally and transversely, their upper faces truncated through- 
out the entire width and length for the articulation of the primi- 
brachs, the articulating facet occupying the middle two-thirds 
of their length; radianal large, pentagonal, resting upon the 
Fig. 1. Diagram of dorsal cup of Cromyocrinus grandis. 
truncated upper angles of the posterior and right posterio- 
lateral basals beneath the right posterior radial, supporting 
upon its truncated upper faces the inter-radianal and anal plates^ ; 
inter-radianal hexagonal, smaller than the radianal, resting 
upon the truncated upper angles of the posterior basal and the 
radianal, between the left posterior radial and the anal plate; 
anal small, pentagonal, resting upon the truncated edge of the 
radianal and situated in part between the inter-radianal and 
the left posterior radial, its upper third projecting beyond the 
margin of the radials; arms and ventral disk unknown. 
The dimensions of the holotype are: diameter of dorsal cup, 
56 mm. ; height of dorsal cup, 37 mm. ; diameter at upper faces 
of the radials, 43 mm. 
