580 GEOLOGICAL SURVEY OF IOWA. 



First radial plate about as long as wide ; two heptagonal and 

 three hexagonal. Second radials short, pentagonal. Third 

 radials turning outwards from, the summit of the second 

 nearly at right angles, seven- or eight-sided, supporting two 

 hrachial plates which give origin to a pair of arms from each 

 ray. Interradials three ; the lower one hexagonal, the two 

 upper ones hexagonal or heptagonal. First anal plate hexa- 

 gonal, as large as the first radial. Second anals smaller, hep- 

 tagonal j a third, fourth and fifth series to the base of the 

 proboscis. 



PLATES of the body ornamented by strong radiating ridges 

 which extend to the margin, and meet corresponding ones 

 on the adjacent plates ; those of the first and second radials 

 terminating in a central node, or transverse nodulose ridge. 

 The ridges of the basal plates proceed around the base and 

 along the margins of each, and a central vertical one joins the 

 curving ridge within : on each side are one or two other 

 abruptly curving ridges, formed by the course of the ridge 

 from the upper to the upper lateral margins of the basal 

 plates. Entire surface granulose. 



Fig. 9. Anterior view of specimen. 



Geological formation and locality. In the Burlington limestone* : Bur- 

 lington, Iowa. 



Actinocrinus multibracliiatus (n. s.). 



PLATE X. FIG. 10. 



BODY subturbinate ; summit depressed-conical, and fur- 

 nished with a strong central proboscis : distance from base 



* If I am right in the identification of this species, I cannot agree with Dr.SnuMARD 

 that it occurs in the "Archimedes limestone"; The bluffs at Quincy ( Illinois), whence 

 he cites his specimens, are of the Burlington limestone; and the Spirifer striatus, large 

 variety, is unknown to me in this locality, the nearest representative being S. grimesi, 

 which is related to S. vowerbyi, and regarded by some geologists as identical with that 

 species. The Actinocrinus (Dorycrinus) mississippiensis can scarcely occur in the bluffs 

 at Quincy; but there is an allied species in the same rock, A. cornigerus. The brachiopod 

 and Crinoid cited occur in a higher position, the Keokuk limestone. 



