98 



OHIO FOSSILS 



b) 



4. a 



8. a 

 b 



9. a 

 b 



10. 



11. 



12. 



13. 



14. 



15. 



16. 



17. a 

 b 



Width greater than height 5 



Beaks large, projecting over margin of shell Girtyella 



Beaks small, not projecting over margin of shell Lingula 



Hinge line wide, shell spiny Strophalosia 



Hinge line narrow, shell without spines Athyris 



Concentric ornamentation stronger than radial ornamentation Leptaena 



Radiating ornamentation stronger than concentric ornamentation 7 



Radiating ornamentation of less than 20 folds or striations 8 



Radiating ornamentation of more than 20 folds or striations 10 



Hinge line more than half as wide as the shell Avonia 



Hinge line less than half as wide as the shell 9 



Shell with 10 or less radial ridges Ptychospira 



Shell with 12 or more radial ridges Camarotoechia, Rhynchopora 



Shell with spines 11 



Shell without spines 13 



Spines small, numerous, aligned in concentric rows Torynifer 



Spines large, few, irregularly distributed on the shell 12 



Radiating ridges continuous Dictyoclostus 



Radiating ridges interrupted Buxtonia 



With sinus and fold 14 



Without sinus and fold 16 



Hinge line as long as width of shell 15 



Hinge line less than width of shell Rhipidomella 



Cardinal area very high Syringothyris 



Cardinal area low Spirifer 



Shell small, with spines on cardinal margin Chonetes 



Shell large, no spines on cardinal margin 17 



Both valves convex Schuchertella 



One valve flat Derbyia, Schellwienella 



Fig. 237 



Orbiculoidea ( Lingulodiscina in older publications) is a survivor from the 

 Devonian (see fig. 237); its nearly central beak is distinctive. O. newberryi is 

 abundant near the base of the Sunbury and very rare in the Logan. 



Girtyella has a large beak on one valve which curls 

 over the beak of the other valve. It has a characteristic 

 outline which separates it from our other Mississippian 

 brachiopods. G. flora (fig. 238) is common in the lower 

 part of the Logan. 



Lingula has already been described in the Devonian 

 chapter (see p. 81 ). L_. melie (fig. 239) is common near 

 the base of the Sunbury and in some parts of the Cuyahoga 

 and Logan. 



Fig. 239 



Fig. 238 



