94 PALAEONTOLOGY OF ILLINOIS. 



GENUS AGARICOCRINUS. Troost. 

 AGAKICOCRINUS NODULOSUS. (sp. nov.) 



PL XIII, Figs. l-la. 



Calyx of medium size, base deeply depressed, the basal de- 

 pression including; the basals, first radials, and the lower part 

 of the second radial plates. All the plates in the basal depres- 

 sion are smoother, and all above are strongly nodose. This 

 species has a tertiary series of radials, smaller than the second- 

 ary, giving; support to the first arm plates, which are also 

 nodose. 



Dome pyramidal, with a series of large, strongly nodose, plates 

 immediately above the arm bases, the number of which is de- 

 termined by the number of arms in the ray. When the ray has 

 four arms, there are three of these plates, two immediately 

 above the base of the arms, and the third above and partly 

 between those below. When the ray has three arms, there are 

 two of these plates, and over the anterior ray, which has but 

 two arms, there is only a single large plate. These plates are 

 succeeded by about three rows of smaller plates, that extend 

 up to the large apical plate which crowns the summit. Anal 

 opening small, and situated just below the apical plate. The 

 anterior ray has two arms, the right anterior and t\vo pos- 

 terior rays four each, and the left anterior three, making seven- 

 teen altogether, which is probably an abnormal number. 



This species may be distinguished from A. americanus, by its 

 tertiary radials, and by the strongly nodose character of all 

 the plates of the calyx, except those included in the basal de- 

 pression. 



Position and locality: Keokuk limestone, Keokuk, Iowa. 



Collector, Mr. L. A. Cox. 



Collection of A. H. Worthen. 



AGARICOCRINUS MACADAMSI. (sp. nov.) 



PL XIII, Figs. 2-2a. 



Calyx large, strongly inflated above the arms, and depressed 

 below, the basal depression including -the entire basal and radial 

 series. 



