ECHINODERMA TA—CRINOIDEA . 541 



133. B. clypeatus (Hall). Mississippic. 

 Calyx wider than long. Dorsal cup higher than ventral disk and 



with concave sides. Plates of calyx flat or moderately convex. 

 Arms 20. 



Burlington of Missouri and Iowa. 



134. B. laura (Hall). Mississippic. 

 Calyx usually higher than wide. Sides of dorsal cup straight or 



slightly concave. All plates of calyx flat and smooth. 

 Upper Burlington of Missouri, Illinois and Iowa. 



135. B. subaequalis (McChesney). Mississippic. 

 Height and width of calyx equal (about one inch). Dorsal cup 



larger than ventral disk, with straight and gradually expanding 

 sides. Plates of calyx nodose or tumid. Arms 22. 

 Burhngton of Missouri, Illinois and Iowa. 



136. B. irregularis Casseday. Mississippic. 

 Small (height about three fourths of an inch), with length 



slightly exceeding width. Dorsal cup deep but not quite the height 

 of the tegmen. Plates of tegmen somewhat nodose. Arms 18. 

 Warsaw of Kentucky and Indiana. 



137. B. icosadactylus Casseday. Mississippic. 

 Width of calyx nearly equal to height (one inch or more). 



Dorsal cup only about half as high as ventral disk, low saucer- 

 shaped, with a protuberant base. Plates of dorsal cup smooth or 

 nearly so ; most of those of ventral disk either thorn-like or spine- 

 bearing. Arms 20. (Type of genus.) 

 Warsaw of Kentucky and Indiana. 



XLVII. Alloprosalocrinus Lyon and Casseday. 



Calyx conical, almost flat below the arm bases, which are in 

 contact laterally except on the anal side, where they are separated 

 by the second anal. Ventral disk conical, passing gradually above 

 into the anal tube which is stout and almost central. 



Especially remarkable for the shortness of the dorsal cup con- 

 trasted with the great height of the ventral disk; in this it resem- 

 bles Agaricocriniis, but difl^ers in the presence of an anal tube. 

 Mississippic. 



