PALAEONTOLOGY OF ILLINOIS. 



Locality and position Lower division of the Burlington group, Bur- 

 lington, Iowa. Lower Carboniferous. No. 283 of Mr. WACHSMUTH'S 

 collection. 



SUBGENUS ZEACEI^US. 

 ZEACROUS SCOBINA, M. and TV". 



PL 1, Fig 2. 

 Zcacrinus scobitia, MEEK and WORTHEN. Proceed. Acad. Nat. Sci., Phila., 1869, p. 149. 



BODY very much depressed, or about four times as wide 

 as high, to the top of the first radial pieces, and concave in 

 the middle below. Base small, and hidden by the column 

 in the concavity of the under side. Subradial pieces curv- 

 ing in to the concavity of the under side, and extending 

 outward around the column ; all presenting a nearly pen- 

 tagonal general outline, with short lateral edges, excepting 

 the one on the anal side, which seems to be hexagonal, 

 (each being without a visible angle at the middle of the 

 under side.) Mrst radials three or four times as large as 

 the subradials, near twice as wide as long, pentagonal in 

 form, with lateral and inferior margins of nearly equal 

 length, and upper edge equaling the entire breadth. Sec- 

 ond radials as wide as the first, and nearly twice as long, 

 all pentagonal in form, the superior angle being salient, 

 and also projecting outward, while a strongly defined me- 

 sial angle extends down the middle of the dorsal or outer 

 side to the base of each, the surface on each side of this 

 angle being distinctly concave. 



Anal pieces small, and owing to the rough surface of the 

 plates, and the indistinctness of the sutures, without very 

 clearly defined outlines. As near as can be made out, the 

 first one seems to be somewhat cuneiform, and wedged in 

 obliquely under one side of the first radial on the right; 

 on its left it connects above the middle, apparently with 

 another resting upon a very short upper side of one of the 

 subradials. Above these other anal pieces are seen be- 



