199 



The interradial and anal series consist of four plates 

 each ; the first heptagonal, as large as the radials or larger, 

 supporting two rather smaller hexagonal plates in the se- 

 cond range, one still smaller in the third, above which the 

 brachial plates of the adjacent rays unite ; the anal series is 

 the same as tho interradial in the best formed specimens ; 

 but there is sometimes a slight irregularity seen in one 

 series, which we infer may be the anal side. Surface of 

 plates flat, or with only the general convexity of the body, 

 covered by very fine confluent granules or interrupted 

 radiating stride, which unite at the sutures ; each subradial 

 plate is marked at the middle of the lower margin with a 

 small triangular node and a somewhat elevated rim, giving 

 a pentalobate border to the basal cavity. Summit, arms 

 and column unknown. 



In general form and the symmetrical arrangement of plates 

 this species has much the appearance of Eucalyptocrinus, 

 but the subradial plates and greater number of interradials, 

 and the absence of the elongate plates separating the pairs 

 of arms as in that genus, are distinguishing characters. In 

 the flatness of the plates, their peculiar surface markings, 

 and their arrangement, this species differs from all others of 

 Rhodocrinus described. 



Geological formation and locality. — In shales of the age 

 of the Niagara group ; Waldron, Indiana. 



GENUS CYATHOCRINUS (Miller). 



Cyathocrinus polyxo (Hall). 



Body broadly turbinate, base somewhat protuberant, sides 

 angular from the prominence of the centres of the sub- 

 radial and first radial plates. Basal plates pentangular, 

 higher than wide, three hexagonal and two heptagonal. 

 First radials large, hexagonal, much wider than high, 

 deeply notched on the upper margin, the articular scar 

 is small and narrow, with the exterior but a little above 



