84 



OHIO FOSSILS 



section of the key. The Devonian pelecypods of Ohio have not received as much attention as 

 the brachiopods, so do not be surprised if you find specimens that do not fit the key - you may 

 have a new record for the state. In collecting pelecypods, both the internal and external 

 molds should be collected when available. Also, open valves, which may show internal 

 characters, should be watched for. The best source for Devonian pelecypod illustrations is 

 Hall (1884, 1885). 



1. 



a) 





b) 



2. 



a) 

 b) 



3. 



a) 

 b) 



4. 



a) 

 b) 



5. 



a) 

 b) 



6. 



a) 

 b) 



7. a) 



b) 



8. a) 

 b) 



9. a) 

 b) 



Key to the Commoner Devonian Pelecypods of Ohio 



(see p. 4 for use of keys ) 



Height and length of shell approximately equal 



(length less than 1. 5 times the height) 2 



Length of shell 1. 5 times or more than 1. 5 times the height .'..'.' 8 



Surface with concentric and radiating ornamentation 3 



Surface smooth or with concentric ornamentation only 6 



Shell with two well developed wings 4 



Shell without wings 5 



Ribs numerous and subequal Aviculopecten 



Ribs few and strong, with smaller ribs between them Cornellites 



Strong ribs on entire surface of shell Conocardium 



Strong ribs on central third of shell only Grammysia 



Shell almost round in outline Paracyclas 



Shell elongate in outline 7 



Shell with an internal ridge from beak to margin 



(forms a groove in internal molds) Nuculites 



Shell without internal ridge Schizodus 



Surface with strong radiating ribs Conocardium 



Surface with concentric ornamentation only 9 



Shell swollen at one end Modiomorpha 



Shell not swollen at one end Sanguinolites 



In Aviculopecten (fig. 186) the shell is not oblique; it is the closest 

 thing we have to a scallop in the Devonian of Ohio. It has both concentric 

 and radiating ornamentation and the ribs, in the commoner Devonian 

 forms at least, are fine and numerous. Several species occur in our 

 Devonian rocks. 



Fig. 187 



Cornellites ( Pterinea in older publications) is similar to Aviculo - 

 pecten but it has widely spaced, strong radial ribs. _C_. flabella 

 (fig. 187) is the common Devonian species. 



Conocardium, as we have 

 already noted, may not be a pele- 

 cypod at all, but since it looks 

 like one and nobody is quite sure 

 just what it is, we have included 

 it here. The hood (fig. 188) is 

 often preserved in our specimens 

 and should be looked for; nobody 



Fig. 18a 



