60 



OHIO FOSSILS 



Fig. 88 



the cup. 7^_ digoniata is common in the Niagaran. 



Holophragma calceoloides (fig. 89) is the only common Silurian coral 

 with a triangular cross-section. This characteristic is not apparent in 

 all specimens but it is obvious in one out of three. The species is common 

 in the Niagaran of Highland County. 



Streptelasma is a common horn coral with septa less than 50 in num- 

 ber. S. radicans (fig. 90) is abundant in the Niagaran. 



Enterolasma caliculum (fig. 91) can sometimes be distinguished from the other horn cor- 

 als because it is extremely thin and long, though small. It is abundant in the Dayton and Euphe- 

 mia. Enterolasma , like Streptelasma , has less than 50 septa, a character which distinguishes 

 them from the next genus. 



Cyathophyllum roadsi (fig. 91a) has more than 90 septa, slightly twisted at the center of 

 the cup. It is common in the Niagaran of Highland County. 



Fig. 89 



Fig. 90 



ig. 91a 



BRYOZOA. In some of the Silurian beds of Ohio, bryozoans are abundant. Ten genera 

 are common enough to be collected frequently. Several rarer ones may also be found. Of these, 

 the first 6 genera have twig-like colonies and the last 4 are leaf-like in appearance. The follow- 

 ing key will help identify them. See Nicholson (1875b) for descriptions. 



Key to the Commoner Silurian Bryozoa of Ohio 

 (see p. 4 for use of keys) 



Colonies twig-like, branching 2 



Colonies leaf-like 7 



Branches hollow in the middle Diamesopora 



Branches • >t hollow in the middle 3 



With monticules Trematopora 



Without monticules 4 



Apertures close together, polygonal 5 



Apertures separated from each other 6 



Walls of apertures thick Eridotrypa 



Walls of apertures thin Monotrypella 



1. 



a) 





b) 



2. 



a) 





b) 



3. 



a) 





b) 



4. 



a) 





b) 



5. 



a) 





b) 



