INVERTEBRATES. 307 



Primary radials three, the first comparatively large, hexagonal or 

 heptagoual, the succeeding ones small, one quadrangular and the 

 other subtriangular, supporting on its upper angles the secondary 

 radial series. 



Secondary radials two, the first quadrangular and the second 

 pentangular, supporting above the two divisions of the arms, giving 

 four arms to each ray. 



The two first arm plates are nearly quadrangular, and longer than 

 those above. The third and fourth are nearly triangular, and are 

 succeeded by a double series of slightly interlocking plates that 

 spread out towards their extremities in the manner peculiar to this 

 genus. 



Interradials three, the first about twice as large as the succeeding 

 ones. Anal series unknown. 



Column at its junction with the body composed of thick, round 

 joints that, a short distance below, are separated by thinner ones 

 arranged alternately. 



Surface of the body plates finely granulose, with a slightly elevated 

 ridge crossing the plates, and extending to the top of the secondary 

 series. 



This species, minus the arms, closely resembles Batocrinus caroli 

 (Hall's sp.) from the same beds, but differs in the number and 

 structure of the arms, that having but sixteen while this has 

 twenty. 



Position and locality: Warsaw beds of the St. Louis group, War- 

 saw, ill. 



No. 2,459, Illinois State collection. 



GENUS ONYCHOCRLNTTS, L. and C. 



ONYCHOCKINUS DISTENSUS, Worthen. 



PL XXIX, Fig. 5. 



Onychocrinus distensus, WOKTHEN, February, 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 31. 



Body of medium size, composed of smooth, massive plates. 

 Basals concealed by the column. 



Subradials on the anterior side sharply angular beyond the col- 

 umnar facet, forming a low, pentagonal cup. 



Radials five, the first pentagonal, about one -fourth wider than 



