78 



OHIO FOSSILS 



Full grown specimens of Siphonophrentis 

 gigantea (fig. 160) are not hard to identify be- 

 cause of their huge size and tube -like cup, but 

 young specimens and the other species of the ge- 

 nus are harder to separate from the more usual 

 cup corals. 



Cystiphyllum (fig. 161) seems to have no 

 septa at all and the cup seems to have started 

 growing all over again several times. This is 

 a rough description for a process called rejuven- 

 ation which occurs in many corals. Several spe- 

 cies are found in the Columbus limestone. 



Heliophyllum halli (fig. 162) is 

 a fine coral with deep, regular cup 

 and many septa. It is the commonest 

 of four species in the Columbus lime- 

 stone. H. proliferum is found in the 

 Tenmile Creek dolomite. 



Zaphrentis is much like Helio- 

 phyllum but has straight septa. Sili- 

 cified specimens, weathered out of 

 the rock, are particularly striking. 

 'L. corniculum (fig. 163) is the com- 

 monest of three species in the Col- 

 umbus limestone. 



Heterophrentis resembles Za- 

 phrentis but the septa have straight, 

 not wavy, edges. Seven species 

 have been recorded from our Mid- 

 dle Devonian, H_. prolifica is the 

 commonest of these. 



In Aulacophyllum (fig. 164) 

 and Cyathophyllum , the septa are 

 numerous (more than 90) and 

 reacnthe center of the cup. Fur- 

 ther separation requires thin sec- '^ 

 tions. Several species of these 

 genera are recorded. 



BRYOZOA. The Devonian 

 forms are rather inconspicuous 

 because of their small size but 

 are well worth looking for. They 

 are abundant in some beds, nota- 

 bly in the shales of the upper part of the Silica formation and 

 in the coral reefs of the Columbus limestone. Nine genera are 

 common enough to be collected frequently but there are several 

 rarer ones not included in the following key. 



Fig. 163 



