CRINOIDS. 199 



Calyx large, ovoid ; basals tali, nearly as high as the ra- 

 dials, which are slightly protuberant at the arm bases. Surface 

 glabrate. 



Horizon and localities — Lower Carboniferous, Lower Bur- 

 lington limestone : Sedalia. 



Platycrinus sampsoni Miller. 



PlatycTinus sampsoni Miller, 1891 : Geol. Sur. Missouri, Bui, 4, p. 13, pi. i, 

 fig. 11. 



Calyx large, cylindrical, rounded below: basal disk shal- 

 low ; radials nearly twice as high as wide ; arm facets rather 

 small. Surface smooth. 



Horizon and localities. — Lower Carboniferous, Burlington 

 limestone : Ash Grove (Greene county), Sedalia ; Burlington 

 ( Iowa ). 



Miller's type is an internal cast in chert and is really too 

 imperfect to deserve recognition. The form is, however, very 

 characteristic and is widely distributed geographically. Speci- 

 mens with the calyx preserved have been found at Burlington 

 and elsewhere. 



Platycrinus americanus Owen & Shumard. 



Plate XXV, figs. 2a-b. 



Platycrinus americanus Owen i<c Shumard, 1850; Jour. Acad. Nat. Sci., 

 Phila.,(2), vol.11, p. 89, pi. xi, tig. 1. 



Platycrinus americanus Owen & Shumard, 1852: Geol. Sur. Iowa, Wiscon- 

 sin and Minnesota, p. 594, pi. vB, fig. 1. 



Platycrinus truncaius Hall, 1858 : Geology Iowa, vol. I, p. 537, fig. 59. 



Platycnnus amabilis Miller, 1891: Geol. Sur. Missouri, Bui. 4, p. 19, pi. il, 

 figs. 9-10. 



Platycrinus broadheadi Miller, 1891 : Geol. Sur. Missouri, Bui. 4, p. 21, 

 pi. ii, fig. 15. 



A form similar to P. burlingtonensis, but smaller, and with 

 the ventral side not so elevated. The sculpturing of the calyx 

 differs greatly in different individuals ; in some specimens the 

 plates are nearly smooth ; in others confluent nodes border the 

 sutures. 



Horizon and localities — Lower Carboniferous, Lower Bur- 

 lington limestone : Sedalia, Louisiana, Hannibal ; Kinderhook 

 (Illinois) ; Burlington (Iowa). 



