80 



OHIO FOSSILS 



It is similar to Fenestrellina but has sharp keels on the branches. Two species are recorded 

 for the Columbus limestone. 



Coscinium is a lace -like bryozoan also but it has no cross-bars like Fenestrellina and 

 Semicoscinium. Instead, the leaf-like colony is pierced by rounded holes. C_. striatum 

 occurs in the Columbus limestone. 



B RACHIOPODA. Our Devonian brachiopods are both varied and abundant. Several gen- 

 era survive from the Silurian into the Devonian but the general aspect of Devonian and Silurian 

 assemblages is distinct enough for easy recognition. The following key will identify the com- 

 moner genera. 



Key to the Commoner Devonian Brachiopods of Ohio 

 (see p. 4 for use of keys) 



1. a) Shell smooth or with concentric markings only 2 



b) Shell with radiating and concentric markings 6 



2. a) Beak on margin of shell 3 



b) Beak near center of shell 5 



3. a) With sinus and fold 4 



b} Without sinus and fold Lingula 



4. a) Height greater than width Meristella 



b) Height and width nearly equal Athyris 



5. a) Beaks near (less than l/3 of shell) the margin Craniops 



b) Beaks far (more than l/3 of shell) from the margin Orbiculoidea 



6. a) Beaks near center of shell Philhedra 



b) Beaks on margin of shell 7 



7. a) Concentric markings stronger than radial markings Leptaena 



b) Concentric markings weaker than radial markings 8 



8. a) With sinus and fold 9 



b) Without sinus and fold 14 



9. a) Hinge line narrow (less than l/3 of width) 10 



b) Hinge line wide (more than l/3.of width) 11 



10. a) Ribs of almost equal size throughout Camarotoechia 



b) Ribs on fold and sinus larger than those on sides Leiorhynchus 



11. a) Fold and sinus weak, inconspicuous Schizophoria 



b) Fold and sinus strong 12 



12. a) Ribs covered with fine radiating markings (really numerous spines) . . Elytha 

 b) Ribs without fine radiating markings 13 



13. a) One beak very large, with a triangular area as high as 



half the width of the shell or more under it Cyrtina 



b) Beaks with low triangular area under them Spirifer 



14. a) Hinge line short (less than l/2 width of shell) I 5 



b) Hinge line wide (more than 1/2 width of shell) 16 



