ECHINODERMA TA—CRINOIDEA . 525 



82. A. multiradiatus Shumard. Mississippic. 

 Size about that of A. verrucosus but ventral disk forming only 



about one fourth of the height of the calyx, and plates of the dorsal 

 cup highly ornamented with strong ridges running in sets of one 

 to four from nodes near the middle of the plates to the margin 

 where they unite with those from adjoining plates. 

 Upper BurHngton of Missouri, Illinois and Iowa. 



83. A. lobatus Hall. Mississippic. 

 Very large. Proportions of calyx much as in ^. lowei, but arm 



bases more prominent, interradial spaces deeper and pit-like, and 

 onamentation of central nodes and parallel ridges more or less 

 obscure. Arms forty. 



Transition between Burlington and Keokuk of Indiana and Illi- 

 nois; Keokuk of Missouri, Illinois and Iowa. 



84. A. lowei Hall. (Fig. 1850.) Mississippic. 

 Large, generally found in crushed condition. Arms eight to 



a ray. 



Keokuk of Missouri, Illinois and Iowa. 



85. A. pernodosus Hall. Mississippic. 

 Large, much like A. lowei, but with smaller arm extensions, 



shallower interbrachial depressions, and lower tegmen. Arms six 

 to a ray. Ornamentation somewhat less symmetrical and central 

 nodes more prominent. 



Keokuk of Illinois, Missouri and Iowa. 



XXXIV. Cactocrinus Wachsmuth and Springer. 



Calyx usually longer than wide, with high ventral disk passing 

 into a strong, nearly central tube. Plates ornamented with nodes 

 and radiating ridges. Plates of ventral disk more or less spinose. 



Differs from Actinocrinus in its more conical, less lobed calyx, 

 with arms in a continuous row around the calyx instead of in 

 clusters. Mississippic (in North America restricted to Kinder- 

 hook and Burlington). 



86. C. glans (Hall). Mississippic. 

 Somewhat larger than C. coelatus and with length proportionally 



greater than width. Suture lines very distinct. Plates flat to 

 nodose; surface smooth or nearly so. Arms 20, very long. 

 Upper Burlington of Missouri and Iowa. 



