206 CRINOIDS. 



Pterotocrinus chesterensis (Meek & Worthen). 



Dichocrinus {Pteroiocrinus) chesterensis Meek & Worthen, 1860: Proc. Acad. 



Nat. Sci., Phila., p. 383. 

 Pterotocrinus chesterensis Meek & Worthen, 1866 : Geol. Sur. IlJinois, vol. 



11, p. 292, pi. xxiii, figs. la-c. 



Dorsal cup basin-shaped, about twice as broad as high, 

 expanding very rapidly from the base to the arm region ; basals 

 two in number, large, concave below ; radials about twice as 

 wide as high, slightly convex. Brachials of the first, second 

 and third orders resting on the upper edge of the radials. Anal 

 plate long, nearly as wide as the radials. Arms four to the ray. 



Horizon and localities. — Lower Carboniferous, Kaskaskia 

 limestone: Chester (Illinois). 



Symbathocrinus wortheni Hall. 



Plate sxv, fig-. 15. 



Symbathocrinus vjortheni Hall, 1858: Geology Iowa, vol. 1, p. 560, pi. ix, 

 fig. 9. 



Calyx small, obconic, truncated dorsally. Basals three in 

 number, forming alow cup. Eadials five, large, quadrangular. 

 Arms very long, slender, composed of quadrangular plates 

 arranged in single rows — the five together forming along tube. 

 Anal plate small, much longer than wide. Stem small, slender, 

 round. 



Horizon and localities. — Lower Carboniferous, Burlington 

 limestone : Springfield, Hannibal. 



Symbathocrinus dentatus Owen & Shumard. 



Plate XXV, flg. U. 



Symbathocrinus dentatus Owen & Shumard, 1852: Jour. Acad. Nat. Sci., 

 Phila., (2), vol. 11, p. 93, pi. xi, fig. 7. 



Symbathocrinus dentatus Owen & Shumard, 1852: U. S. Geol. Sur. Wis- 

 consin, Iowa and Minnesota, p. 597, pi. vB, figs. 7a-b. 



Very much like S. wortheni, but much larger and more 

 robust. 



Horizon and localities.— Low^v Carboniferous, Burling- 

 ton limestone : Columbia, Springfield, Ste. Genevieve. 



