Table III. — Continued. 



AD 

 L 



(Distance anterior to extremity from a line passing through median dorso-ventral 



plane of value.) 



Greater Value in Upper 

 Ohio Drainage. 



Species with Even No. Cases. 



Greater Value in L. Erie. 

 L. ovala (3-4) 



PHL 



(Length of shell compared with posterior hinge-line.) 



Greater Value in Upper 

 (Jhio Drainase. 



Species with Even No. Cases. 



Greater Value in L. Erie. 



AHL 

 L 



(Length of shell compared with anterior hinge-line.) 



Greater Value in Upper 

 Ohio Drainage. 



Species with Evan No, Cases. 



Greater Value in L. Erie. 

 Proptera (4) 



TH 



DVD 

 (Thickness of shell divided by dorso-ventral diameter.) 



Greater Value in Upper 



Ohio Drainage. 

 Amblema (2) 



Pleurobema (3-5) 



Proptera (4) 



A. ferussacianus (3-4) 

 Symphynola (2) 



Eurynia (2) 



L. luteola (2-3) 



Species with Even No. Cases. 



Greater Value in L. Erie. 



