ECHINODERMATA—CRINOIDEA. 



519 



62. P. halli Shumard. (Fig. 1840.) Misslssippic. 

 Interradial sutures slightly depressed, giving to the cup a some- 

 what five-sided outline. Arms 7 or 8 in each ray, short and heavy. 



Burlington of Missouri and Iowa. 



63. P. discoideus Owen and Shumard. Mississippic. 

 Like P. siibspinosus in general form. Calyx in proportion to 



arms, much larger and surface of plates deeply corrugated. 

 Burlington of Missouri, Iowa and New Mexico. 



64. P. subspinosus Hall. (Fig. 1841.) Mississippic. 

 Dorsal cup discoid, almost flat to the middle of the R and thence 



curving upward. Arms spreading almost horizontally outward and 

 recurving over the disk. Plates smooth or only obscurely cor- 

 rugated. 



BurHngton of Missouri, Iowa and New Mexico. 



65. P. bonoensis White. Mississippic. 

 Dorsal cup wider than high, bowl-shaped and spreading. Plates 



Fig. 1842. Platycrinus hemisphericus, FiG. 1843. Platycrinus huntsvillcE, 

 calyx with arms, with Igoceras pabulocri- (After Troost and E. Wood.) 

 num attached. (After Keys. ) 



slightly convex centrally, smooth. Arms five or six in each ray, 

 short and stout, and closely packed. Smaller and stouter than F. 

 huntsvill(£. 



Keokuk and Warsaw of Indiana and Missouri. 



