5 8 OHIO FOSSILS 



Key to the Commoner Silurian Corals of Ohio 



(see p. 4 for use of keys ) 



Animals in colonies of many individuals 2 



Animals solitary, horn-shaped 10 



Tubes arranged in parallel masses 3 



Tubes arranged in chain-like series Halysites 



Colonies branching or leaf -like Coenites 



Colonies hemispherical or honeycomb -like 4 



Tubes polygonal in outline 5 



Tubes round or elliptical in outline 7 



Tubes large, some as much as 3/8 inch in diameter Arachnophyllum 



Tubes smaller than 3/16 inch 6 



Walls of cup thin Favosites 



Walls of cup thick Thecia 



Edges of tubes not touching 8 



Edges of tubes touching 9 



Cups joined together by numerous crossbars at right angles Syringopora 



Cups not joined by crossbars but budding from each other at acute angles. . Fletcheria 



Main, round, cups separated by smaller polygonal cups Heliolites 



Main cups touching, not separated by smaller, polygonal cups Lyellia 



Septa prominent, numerous 11 



Septa not prominent; cup with numerous blister-like growths Cystiphyllum 



Most of septa reach center of , cup 12 



None of septa reach center of cup Amplexus 



Septa with wavy edges 13 



Septa with straight edges 14 . 



Septa slightly twisted at center Heliophyllum 



Septa straight throughout Zaphrentis 



Cup somewhat triangular in outline Holophragma 



Cup circular in outline 15 



Septa less than 50 Streptelasma and Enterolasma 



Septa more than 90 Cyathophyllum 



The following descriptions are arranged in the same order as the key. The characters 

 used in the key are not all repeated in the descriptions. The colonial forms are discussed 

 first, then the solitary or horn corals. 



Halysites is unique among the colonial forms. It has been well named "chain coral" for 

 its tubes are arranged in rows in a chain-like network which is strikingly apparent in weath- 

 ered specimens or in natural sections. H. catenularia (fig. 81) and 1L labyrinthica are com- 

 mon in some parts of the Niagaran. 



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