JOi. CONTRIBUTION TO 



From G. kentiiekiensis this species differs in the number of arms, (thirty 

 instead of forty) the less number of radiating ridges on the cal3'^x plates, and 

 the strong nodose character of the first radials. 



Tlie specimens figured come from the Upper Devonian beds near Charles- 

 town, Ind., and are the ])roperty of Mr. G. K. Greene. 



A O R O C R I N U S ( A S S E I) A Y I , Lyon, Rowley. 



Plate 32. J'^igs. 7, 8, 9. 



The three basal plates form a wide, thin, continuous rim below the radials, 

 the body being constricted above. 



Tlu' first radials are hexagonal, the second hexagonal, the third pentagonal. 



Tlicre are two radials of the second series (secondary brachials). Each 

 ray of the third radial series is composed of two plates. 



The first interradial is hexagonal with two plates above and two other 

 very snuill ones above the latter. 



The first anal plate is seven-sided and as large as the first radial. 



Above this plate are three tuberculose plates, five smaller tuberculose plates 

 above the latter, and four or five yet higher up. 



All the calyx plates are highly convex and are made stellate by short, ra- 

 diating ridges, extending to the sutures. 



The arm lobes are strong, the column is small, the canal minute. 



The ventral disk is somewhat elevated, but less so than the dorsal cup. 



The plates are small and convex or warty. 



The food grooves are covered by a double row of small, warty plates. 



Over each pair of arm openings is a quite strong, low, warty-like tubercle. 



The central dome plate supports a short, heavy, spine-like tubercle. 



The anal opening is lateral, directed outward and on a flattened ridge. 



The arm openings are directed a little upward and twent3^-two in number, 

 the right anterior lobe bearing six against four for each of the other lobes. 



This ])eautiful fossil comes from the Upper Devonian, near Charlestown, 

 Ind.. and the specimen figured is the property of Mr. G. K. Greene. 



A study of the figures of Gennteocrinus facetus and Aorocrinus cassedayi, 

 on our plate, will fail to bring out the great differences between the two genera, 

 as seen by Wachsnnith and Springer. The anal opening in Gennieocrinus is 

 much nearer the i)eriphery than described and from a mere opening through 

 the vault, is really, when well jireserved, on a wart-like protuberance. There is 

 also a large central node on the dome, corresponding to the spiniferous node on 



