9 8 



NORTH AMERICAN INDEX FOSSILS. 



corallites slightly larger than in preceding, and somewhat more 

 distant. Pseudosepta nearly reaching the center in well-preserved 

 specimens. Microcorallites polygonal. 





Fig. 157. Heliolites elegans (N. Y. Geol. Surv. ). 



In the Niagara group of Michigan, Indiana, Kentucky, Ten- 

 nessee, etc. 

 128. H. elegans Hall. (Fig. 157.) Siluric. 



Hemispheric coralla with macrocorallites a little over .5 mm. in 

 diameter, and pseudosepta in the form of 

 oblique spines and reaching half way to the 

 center. Microcorallites crowded, minute. 



In the Niagara group of New York, 

 Michigan, Indiana, Kentucky, etc. 



XLVII. Plasmopora E. & H. 

 Differs from Heliolites in having twelve 

 well-developed vertical rows of spinulose 

 pseudosepta and ccenenchyma composed of 

 intersecting plates which however form no true 

 microcorallites, and whose tabulae become 

 more or less continuous, producing a vesicular tissue. Ord?-Dev. 



129. P. follis E. & H. (Fig. 157, c, d.) Siluric. 



Tubes from I to 1.5 mm. in diameter with circular crenulated 



Fig. 158, a, 6. Helio- 

 lites interstinctus ; c, d, 

 Pla sm op or a follis , v e r ti cal 

 and horizontal sections 

 enlarged (after Lambe). 



