54 NORTH AMERICAN INDEX FOSSILS. 



*** Heads with larger round corallites scattered among smaller angular, often 



minute ones. Tabulae numerous 7-j- 



7f Septa absent ; mural pores present XXXV. Favosites 



7| Septa present in large corallites, 12 in number; no mural pores / 



p. Septa 12 infoldings of wall, short XLVI. Heliolites 



p. Septa well developed, spinulose, smaller corallites imperfect, vesicu 



lose in tissue XLV1I. Plasmopora, 



D. Corals compound, forming branching stems or expansions with numerous calices 



scattered over the surfaces **#■* 



■*tt-K# Ccenenchyma separating calices 8f. 



8f Calices regular, septate q. 



q. Columella papillose, ccenenchyma dense 7. 



7. Branches cylindrical, calices spirally arranged. LVII. Oculina. 

 7. Branches irregular, often flattened and expanded. Calices 



scattered L V III. Astrohelia. 



**** Branching; ccenenchyma absent 9-j-. 



9f Calices distinct, with septal striae surrounding the orifice. 



r. Thick-walled with circular openings, distant superficially. 



XLIII. Trachypora. 

 r. Thick-walled, circular orifices in polygonally depressed calices. 



XLII. Striatopora. 



9f Corallites without septal striae s. 



s. Corallites thin-walled, openings oblique, crowded, generally curved 



on one side XL. Alveolites. 



s. Corallites thick-walled, orifices irregular, distant XLI. Cladopora. 



s. Corallites opening regularly with polygonal or rounded crowded aper- 

 tures. Mural pores in regular rows, tabulae numerous. 



XXXV. Favosites. 



Tetrameral Corals. 



I. Streptelasma Hall. 



Simple conical corals, generally curved, with a funnel-shaped 

 calyx, which is generally deep and furnished with numerous septa, 

 the longer of which are in some species twisted at the center. 

 Fossula present in later types. Tetrameral arrangement of septa 

 shown by their external ends. Epitheca thin. Interior marked 

 by tabulae. Ord.-Dev. 



1. S. profundum (Owen). (Fig. 76, a-b.) Lower Ordovicic. 



Deep calyx and few septa, the septa not twisted at the center, 

 and strongly crenulated in their margins. Primary septa strong 

 and three pseudo-fossulae well developed, formed by union of ends 

 of septa next to cardinal and alar septa. Cardinal one double and 

 divided by cardinal septum. 



In beds of Black River, Chazy, and doubtfully Beekmantown 

 age, Michigan, Wisconsin, Iowa, New York, Canada, etc. 



