278 New Species of Crinoidea from the 



plates, truncate at base. Basal plates short, scarcely thick- 

 ened at the lower margins, projecting but little beyond the 

 column. First radial plates of moderate size. Second 

 radial plates varying from quadrangular to hexagonal. 

 Third radial plates usually larger than the second, varying 

 from pentagonal to heptagonal, wedge-form above, and 

 supporting on each upper side a bifurcating supra-radial 

 plate, on the outer side of which rests a series of brachial 

 plates, and on the inner side a supra-radial of the second 

 order ; this supports brachial plates on each side, making 

 the brachial formula « ir :== 30. 



Interradial series consisting of four or five plates each, 

 the first large, seven-sided, supporting two smaller plates 

 in the second range, one seven-sided and one six-sided, 

 with one or two small plates above. The anal series con- 

 sists of seven or eight plates ; the first hexagonal, little 

 smaller than the first radial plates, supporting two in the 

 second range, little smaller than the first interradial plates ; 

 three in the third range ; with the others irregularly placed 

 above. Dome and arms unknown. Sm'face of body plates 

 elevated into strong angular nodes, sometimes marked by 

 low ridges in the lower part ; the nodes of the upper part 

 connected by a strong angular ridge. 



This species is of the type of A. mullibrachiatus, (Iowa 

 Geol. Rep. pi. 10, fig. 10 ;) but differs in its spreading form 

 and ansrular nodes. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of C. A. White. 



Actinocrinus ventricosus var. internodius. Actinocrimis 

 ventricosus (Geol. Report of Iowa, Vol. I. part II. page 

 595, pi. 11, fig. G). 



A specimen recognizable by its structure and arrange- 

 ment of })lates, nuniljer of arms, etc., as of tliis species, 

 presents some peculiarities of surface markings. The 

 basal plates are extended laterally in a deeply crenulated 



