46 OHIO FOSSILS 



colonies, in the Richmond, especially the upper part. Protarea richmond - 

 ensis is unlike the other colonial corals. It grows in crusts over fossils and 

 pieces of rock, not in hemispherical colonies. The cups have septa which 

 give the edges of each cup a beaded appearance. It is found in the Richmond. 



Fif. so BRYOZOA . A bewildering abundance of bryozoans is found in the Ordo- 



vician rocks of Ohio. The surest way to identify them is to prepare thin slices for microscopic 

 examination. Still, some forms may be recognized more or less certainly by their external 

 characters. They are divided, according to the outer appearance of the colonies, into twig- 

 like forms and fan- or sheet-like masses. 



Key to the Commoner Ordovician Bryozoa of Ohio 



(see p. 4 for use of keys ) 



1. a 

 b 

 c 

 d 



2. a 

 b 



3. a 



b 



4. a 

 b 



5. a 

 b 



6. a 

 b 



7. a 

 b 

 •c 



8. a 

 b 



9. a 

 b 



10. a 

 b 

 c 



11 a 

 b 



Colonies twig-like, cylindrical, branching 2 



Colonies twig-like, not branching Escharopora 



Colonies twig-like, flattened or expanded 7 



Colonies fan- or sheet-like 8 



With monticules 3 



Without monticules 4 



Monticules numerous Hallopora (except H. oneilli) and Homotrypa 



Monticules few Dekayella 



Branches small (diameter about 1/16 inch) Hallopora oneilli 



Branches large (diameter about l/4 inch or more) * 5 



Tubes of moderate size 6 



Tubes very small, making the branches look almost smooth Bythopora 



Tubes almost square in cross-section Rhombotrypa 



Tubes round in cross -section Batostoma 



Without monticules Dekayia, Chiloporella, and Homotrypa flabellaris 



Without monticules but with maculae Homotrypa obliqua 



With monticules Homotrypa dawsoni 



With monticules 9 



Without monticules 10 



Monticules star-shaped Constellaria 



Monticules not star -shaped Monticulipora and Heterotrypa 



Colonies disk-like 1 1 



Colonies fan -shaped, with tubes on both surfaces Peronopora 



Colonies a network of tubes Stomatopora 



Colonies low and irregular in outline Aspidopora 



Colonies hemispherical Homotrypella 



Fig. 51 



Some bryozoans have a relatively flat surface; in others, groups of tubes 

 are higher than others, forming bumps called monticules (see fig. 51) on the 

 surface of the colony, which are useful in separating the genera from each other. 

 Others have groups of tubes smaller than the others which form spot-like marks, 

 called maculae (see fig. 52) on the surface. 



