60 [Assembly 



origin, and the outer brancli again bifurcating, while the inner 

 one continues simple. The bifurcations of the postero- lateral 

 rays have not been determined. In the anterior ray, the second 

 radial plate is truncate above, and supports a single arm, which 

 divides on the fifth plate above the second radial, and again on 

 the tenth plate in one division and on the twelfth in the other ; 

 above which, it continues simple. 



Arms rounded on the back, composed of a single series of very 

 short plates. Anal plates unknown. 



Surface of the plates nearly smooth, or with arching lamellose 

 striae. 



Column small, round, composed near the body of thin alternately 

 larger and smaller plates. Arms much swollen at the bifurca- 

 tions. 



This species closely resembles the Z. scoparius of the Burlington limestone in its 

 general features and the bifurcation of the arms; but differs in having a more 

 spreading calyx, and a much greater proportional length of the arms, the plates of 

 which are thicker, and not flattened on the back as in that one. The anterior ray 

 also differs in that one, having but two plates between the second radial plate and 

 the first bifurcation. 



ZEACRINUS MEROPE (n.s.). 



Body small, very broadly turbinate, subangular above from the 

 prominence of the second radial plates. Basal plates small, 

 triangular : subradial plates about equal in length and breadth. 

 First radials much wider than high : second radials about as 

 wide as high, constricted in the middle and angulated longitu- 

 dinally, each one of them supporting a pair of arms which rise 

 from the upper sloping faces of the plate. In the antero-lateral 

 rays, the arms bifurcate on the sixth and eighth plates from 

 their base ; the outer division again bifurcating on the tenth 

 plate above the first division, and the inner division continuing 

 simple throughout. In the anterior ray, the second radial plate 

 is truncate above ; and the second plate above that one becomes 

 a bifurcating plate, supporting two arms Avhich bifurcate on 

 the tenth plate above their origin. Anal plates small. 



Arms composed of short wide equal-sided plates, which are an- 

 gular on the back. The plates of the body are marked by in- 

 distinct radiating ridges, which show a tendency to become 

 nodose. Second radial plates strongly angular, and subcarinate 

 along the middle. 



The surface of the plates of the arms is striato-granulose. 



Column, near the body, composed of thin unequal plates, and 

 showing a tendency to become subangular below. 



This species differs from the Z. paternus in the turbinate form of the calyx, the 

 angulated and sculptured surface of the body, and the subangular form of the arms. 

 In the anterior ray, it differs in the division of the arms taking place on the fourth 

 radial, instead of the seventh as in that one. 



