534 PALAEONTOLOGY OF ILLINOIS. 



SUB-GENUS SCAPHIOCKQOJS. 

 SCAPHIOORINUS HUNTSVILL^E, Wortheu Ms. 



PI. 20, Fig. 1. 



BODY small, cup-shaped, gently swelling from the base 

 to the top of the first radials. Basal plates minute and 

 hidden beneath the upper joint of the column. Sub-radials 

 rather small, about as wide as long, and hexagonal so far 

 as they are shown in the specimen under examination. 

 First radials wider than high, second radials higher than 

 wide, constricted on their sides, and gradually swelling to 

 the base of the acute angle at their summits, where they 

 give support to a pair of arms composed of wedge- formed 

 pieces. Some of the arms continue single to their extremi- 

 ties, while others bifurcate on the eighth and tenth plates 

 above the second radials, and all give oif pinnula3 from their 

 inner margins. 



This species is somewhat closely allied to 8. decabracMatus, of Hall, 

 but differs essentially in the bifurcation of the arms. 



Position and locality St. Louis Limestone? near Huntsville, Ala- 

 bama. 



SUB-GENUS ZEAOKIKUS. 

 ZEACRINUS ARBOREUS, Worthen Ms. 



PI. 20, Fig. 5. 



BODY small, depressed basin-shaped below the top of 

 the first radials. Base deeply concave, concealing the 

 minute basal plates in the cavity occupied by the columnar 

 facet. Sub-radials about as w T ide as long, four hexagonal 

 and one heptagonal, the one on the anal side a little larger 

 than the others, and supporting on its upper angle an anal 

 piece about half its own size, above which are two more of 

 nearly the same size, and all pentagonal. Eirst radials 

 wider than high, slightly beveled on their upper margins, 



