ECHINODERMATA—CRINOIDEA. 521 



suture running from the anal plate to the anterior R. R large, 

 subequal, except the anterior which is pentangular. Costals two 

 to a ray, short and narrow. Arms thin, sometimes pendent. Pin- 

 nules very long. Anus excentric, at end of a protuberance or tube. 

 Column round. Mississippic. 



70. D. ficus Lyon and Casseday. Mississippic. 



Plates smooth except for a slight median angularity of the R. 

 B forming a deep conical cup. Arms 20, recurving. 



Keokuk of Kentucky, Indiana, Missouri and Iowa. 



Fig. 1845. a, Dichocrinus polydadylus, side view; b, basal view of var. (After 

 Meek and V/orthen.) 



71. D. polydactylus Lyon and Casseday. (Fig. 1845, ^^ ^0 



Mississippic. 



R and anal very convex. Plates ornamented with scattered 

 nodes. Arms eight in each ray. 



Keokuk of Indiana. 



'J2. D. striatus Owen and Shumard. Mississippic. 



Calyx subglobose. Plates thickly covered with conspicuous lon- 

 gitudinal ridges forming six rhombs around the calyx. 



Burlington of Missouri, Illinois and Iowa. 



73. D. inornatus Wachsmuth and Springer. (Figs. 1846, 1806, d) 



Mississippic. 



Plates unmarked except with a faint angularity along the center 

 of the R. 



Kinderhook of Iowa. 



