204 CRINOIDS. 



Horizon and localities. — Lower Carboniferous, Upper Bur- 

 lington limestone : Ash Grove. 



Dichocrinus ficus Casseday & Lyon. 



Dichocnnus ficus Casaeday & Lyon, 1860 : Froc. Am. Acad. Arts and Sci., 



vol . V, p . 24. 

 Dichocrinus ficus Meek & Worthen, 1873: Geol. Sur. Illinois, vol, V, p. 



500, pi. xiv, fig. 2. 

 Dichocrinus coxanus Worthen, 1882: Illinois State M.U8. Nat. Hist., Bui. 1, 



p. 35. 

 Dichocrinus coxanus Worthen, 1883: Geol. Sur. Illinois, vol. VII, p. 313, 



pi. xxvii, fig. 7. 

 Dichocrinus parvulus Miller, 1891: Geol. Sur. Missouri, Bui. 4, p. 27, 



pi. iv, figs. 7-8. 

 Dichocrinus humbergi Miller, 1891 : Geol. bur. Missouri, Bui. 4, p. 26, pi. iii, 



figs. 9-10. 

 Dichocrinus humbergi Miller, 1891 : Geol. Sur. Indiana. ITth Ann. Rep. , adv. 



sheets, p. 36, pi. vi, fig. 38. 



Calyx higher than wide, somewhat conical. Basals two in 

 number, of equal size, forming about one-half of the dorsal cup. 

 Badials very large, oblong, with well-detined articular facet, for 

 the support of the brachials, which occupies about one-half 

 the width ; costals very small, the second supporting two arms. 

 Arms slender, biserial ; pinnules long and stout, two to the 

 ray. Anal plate very large, similar to the radials and in the 

 same circlet. Ventral side flattened. Surface of plates smooth. 

 Stem circular. 



Horizon and localities. — Lower Carboniferous, Keokuk lime- 

 stone : Boonville ; Keokuk (Iowa). 



The species of Dichocrinus are readily mistaken for those 

 of Platycrinus, but may easily be distinguished by having two 

 basal pieces instead of three, as in the latter genus, and in 

 having six large plates in the second circlet instead of five. In 

 most of the species of this genus rarely more than the dorsal 

 cup, or the anchylosed basals, are found, and hence the group 

 usually escapes the notice of the majority of collectors. D. 

 Jicus seems to be a rather widely distributed species and admits 

 of considerable variation throughout its range. It was first 

 described from Indiana by Casseday and Lyon in 1860; and 

 since that time has been recognized in several other localities 

 where the Keokuk rocks are exposed. D. coxanus of Worthen 



