CRINOIDS. 201 



cup. Ornamentation similar to P. saffordi, but with the tuber- 

 cles covering the plates and arranged in concentric rows around 

 the column and arm-bases. 



Rorison and localities. — Lower Carboniferous, Lower Bur- 

 lington limestone : Sedalia. 



Platycrinus halli Shumard. 



Plate XXV, flg. 3. 



Platycrinui planus? Hall, 185S : Qeol. Iowa, vol. I, p. 533, pi. viii, tigs. 



6a-b. 

 Platycriiius halli Shumard, 1865: Trans. St. Louis A.cid. Sci., vol, II, 



p. 388. 

 Platycrinus halli Meek & Worthen, 1875: Gaol. Sar. Illinois, vol. V. p. 



454, pi. iii, figs. 3-3d. 

 PlatycHnus acclivus Miller, 1891: Geol. Sur. Missouri, Bui. 4, p. 12, pi. i, 



figs. 9-10. 



Calyx large, subglobose, heavy; basal cup bowl- shaped, 

 with columnar scar circular ; radials a little higher than wide ; 

 ventral side hemispherical, composed of large, heavy plates 

 which are convex externally ; arms 12 to 16 to the ray. Sur- 

 face smooth, or occasionally with indistinct folds or obtuse 

 ridges. 



Horizon and localities. — Lower Carboniferous, Upper 

 Burlington limestone : Ash Grove (Greene county) ; Burling- 

 ton (Iowa). 



Platycrinus bonoensis White. 



Platycrinus bonoensis White, 1879: Proc. A.cad. Nat. Sci., Phila.,p. 30. 

 Platycrinus bonoensis White, 1883: U. S Geol. & Geog. Sur. Terr., 12 



Ann. Rep., p. 160, pi. xl, fig. 5a. 

 Platycrinus oeternalis Miller, 1891: Geol. Sur. Missouri, Bui. 4, p. 11, 



pi. i, fig. 8. 



A small form with smooth, bowl-shaped calyx, stout arms, 

 six to the ray, and heavy stem. 



Horizon and localities. — Lower Carboniferous, Keokuk 

 limestone: Boonville. 



G— 14 



