CHAPTER yil. 



BCHINODBRMS: CYSTIDS AND BLASTOIDS. 



Comarocystites shumardi Meek & Worthen. 



Plate xviii , fig . 2 . 



Comarocystites shumardi Meek & Worthen, 1865: Proc. Acad. Nat. Sci., 



Phila., p. 143. 

 Comarocystites shumardi Meek & Worthen, 1868 : Geol. Sur. Illinois, vol. 



Ill, p. 292, pi. i, figs. la-b. 



Calyx obovate, height slightly more than width. Basals 

 wider than long, rather irregular in shape ; succeeding ranges 

 of plates very irregularly arranged and differing in form, but 

 increasing in size upward, chiefly hexagonal and heptagonal ; 

 all deeply concave externally, with prominent ridges at the 

 sutures. 



Horizon and locality — Lower Silurian, Trenton limestone : 

 Cape Girardeau. 



Comarocystites obconicus Meek & Worthen. 



Plate xviii, fig. 1. 



Comarocystites shwnardi var. obconicus Meek & Worthen, 1865: Proc. Acad. 



Nat. Sci., Phila., p. 144. 

 Comarocystites shumardi var. obconicus Meek & Worthen, 1866 : Geol. Sur. 



Illinois, vol. Ill, p. 294, pi. i, figs. 2a-b. 



Calyx closely resembling C. shumardi, but smaller and 

 longer. 



Horizon and locality. — Lower Silurian, Trenton lime- 

 stone : Cape Girardeau. 



