198 



form of the two upper interradials when united, but 

 smaller ; the summit reaches as high as those plates. 



This species is extremely variable in form and proportions 

 of the body; the older specimens are often more elongate, 

 sometimes constricted near the middle of the cup, giving a 

 concavity to the sides. The base is sometimes much broad- 

 er, and in some specimens giving to the first radials a greater 

 proportional breadth. It differs from the E. Icevis and E. 

 phillipsi of Troost, in the much greater height of cup, greater 

 elongation of plates, and in having a less proportion of the 

 first radial plates within the basal cavity. 



Geological formation and locality. — In shales of the age of 

 the Niagara Group ; Waldron, Indiana. 



GENUS RHODOCRINUS (Miller). 



RHODOCRINUS MELISSA (Hall). 



Body depressed, subspherical, or nearly hemispheric, base 

 nearly flat or very depressed convex, central basal cavity 

 abruptly and deeply depressed ; sides inflated in the lower 

 part and contracted just below the arm bases, where it 

 is again a little expanded. Basal plates very small, con- 

 cealed within the basal cavity and covered by the column. 

 Subradial plates elongate heptagonal, their greatest width 

 about one-third above their lower margin. Radial plates 

 proportionally large ; the first pentangular, wedge form 

 below, the second hexagonal, as large as the others ; 

 the third usually hexagonal (sometimes pentagonal), sup- 

 porting a series of two large supraradial plates, with a 

 very small bifurcating or axillary plate resting in an exca- 

 vation in the middle of the upper margin of the second ; 

 above which commence the first arm plates, resting part- 

 ly on this small plate, and partly on the second suprara- 

 dial plate. Above the third radial, and resting on its 

 upper margin there is a somewhat large, heptagonal in- 

 tersupraradial plate. 



