534 NORTH AMERICAN INDEX FOSSILS. 



2. Plates of ventral disk mostly convex or tumid c. 



3. Calyx pyramidal III. A. pyramidatus. 



3. Calyx depressed pyramidal 112. A. bullatus. 



109. A. brevis (Hall). Mississippic. 



Small and delicate. Dorsal cup and tegmen of same height. 

 All plates below the arms nodose and with short ridges at the 

 sides where they meet ridges from adjoining plates. 



Lower Burlington of Missouri, Illinois and Iowa. 



no. A. planoconvexus (Hall). Mississippic. 



Agreeing with A. bullatus in size and in the low convexity of 

 the tegmen, but all plates of the tegmen and dorsal cup except the 

 posterior oral flat. 



Lower Burhngton of Missouri and Iowa. 



111. A. pyramidatus (Hall). Mississippic. 

 Small, pyramidal. Arm facets almost confluent. Arms 10. 

 Lower Burlington of Missouri and Iowa. 



112. A. bullatus Hall. (Fig. 1861.) Mississippic. 

 First interbrachials very large, sometimes twice the size of the 



S 





■ f 



Fig. 1 861. Agaricocrinus bullatus, Fig. 1862. Agaricocrinus iuberosus, 

 basal and anal view. (After Hall. ) anal side. (After Hall, Iowa Geol., 



I., 2.) 



R, followed by two long and very narrow pieces which reach to 

 the level of the arm openings. Anal area wide and flat. Column 

 small. 



Upper Burlington of Missouri, Illinois and Iowa. 



113. A. americanus Roemer. Mississippic. 



Like A. tuberosus in general outline, but calyx less con- 

 cave below, first interbrachial longer, rising to the top of the dorsal 



