514 



NORTH AMERICAN INDEX FOSSILS. 



53. E. typus Meek and Worthen. Carbonic. 



Calyx basin-shaped, rounded below, with outline somewhat five- 

 angled as seen from above or below. 

 Plates smooth and slightly convex. 



Carbonic of Illinois, Nebraska and Utah. 



XXIII. Agassizocrinus Troost. 

 Attached in larval state, free-swimming 

 in adult. Dorsal cup elongate, with massive 

 plates. IB and B very large, the former 

 consisting of five elongate pieces which 

 form an almost solid semi-globose body, 

 with suture lines nearly or quite obliterated. 

 R very short, wider than high. Anal and 

 radianal both present. Arms 10, long and 

 stout. Column absent in adult. Kaskaskia 

 of North America. 



54. A. dactyliformis Shumard. (Fig. 

 Fig. 183 1. Agassizocri- 1 83 1.) Mississippic. 



nus dactyliformis. (After ^^^ obconical, with CUrved sides. 

 Roemer. ) 



Kaskaskia of Arkansas and Illinois. 



55. A. conicus Owen and Shumard. (Fig. 1832.) Mississippic. 



Elongate-conical, narrower and with more pointed base than 

 A. dactyliformis. 



Kaskaskia of Illinois. 



XXIV. Edriocrinus Hall. 

 Attached in larval state, free in adult. IB 

 absent. B very large and elongate, closely 

 anchylosed, with suture lines obliterated. 

 Base in young irregular and linear, in adult 

 deeply bowl-shaped, with scar of attachment 

 obliterated by calcareous deposits. B fol- 

 lowed by 5 R and an anal plate. R compara- 

 tively small, quadrangular; articular facets 

 but slightly excavated, occupying the full 

 width of the plates, and with a sharp articular ridge. Anal plate 

 supporting a second small plate. Arms broad at base, composed 

 of extremely short transverse pieces. Devonic. 



Fig. 1832. Agassizo- 

 crinus conicuSy basal por- 

 tion. (After Meek and 

 Worthen, Geol. 111., V.) 



