34 



Family POTERIOCRINIDiE. 



ZEACRINUS BELLTJLTJS, n. Sp. 



Plate III, Fig. 8, calyx and arms, azygous side on the left. 



Species below the average size, slightly constricted above the 

 calyx, arms coming to a point at the summit, and the whole 

 very neat in outline. Calyx low; plates convex; sutures bev- 

 elled; columnar cavity moderately deep; surface granular. 



Basal plates within the calyx and covered externally by the 

 column. Subradials rather large, barely visible, at the superior 

 angles in a side view, convex and sutures distinct. First radials 

 wider than high, convex, truncated the entire width above and 

 separated from the second radials by a gaping su ure. Second 

 radials nearly as long as wide, convex longitudinally, depressed 

 laterally toward the sutures, pentagonal, axillary and support- 

 ing upon each upper sloping side a single arm. However, the 

 ray opposite the azygous area is not visible in our specimen, 

 and it may, as in other species in this genus, bear only a single 

 arm, and hence the species will possess only nine arms; but if 

 it is like the other rays, the species has ten arms. 



The arms are slightly fusiform and composed of a single series 

 of plates which are transverse and nearly as long as wide, at 

 first, but gradually become thinner and wider and cuneiform 

 toward the middle part, and, without again shortening, they 

 become narrower as the arms taper to the distal end. Each 

 plate bears a pinnule directed upward and inward and com- 

 posed of long joints. 



The first azygous plate is twice as long as wide, has five sides, 

 the lower end abuts upon a subradial, the under sloping side 

 rests upon another subradial, and the upper sloping side abuts 

 upon the under sloping side of the first radial on the right; 

 one superior side abuts the second azygous plate, while the 



