74 NORTH AMERICAN INDEX FOSSILS. 



56. D. caespitosum Hall. (Fig. 117.) Siluric. 



Fig. 115. Synaptophyllum simccense (Ind. Geol. Surv.). 



FlG. 116. Synaptophyllum sir amineum (Ind. Geol. Surv.). 



Slender cylindrical stems with a broad central tabulate, and a 

 narrow peripheral zone. Septa thin, reaching the center. 



