350 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE IV. 



All figures are three-fourths natural size, a, lateral view; h, dorsal view. 



Fig. L Quadrula quadrula (Rafinesque). Only specimen ever found in the Ohio 

 in Pennsylvania, from Ohio River, Cook's Ferry, Beaver Co., Pennsylvania, collected 

 September 10, 1908; C. M. Cat. No. 61.3869. 



Fig. 2. Quadrula verrucosn (Rafinesque). Male of medium size, from Shenango 

 River, Pulaski, Lawrence Co., Pennsylvania, collected July 19, 1909; C. M. Cat. No. 

 61.4121. 



Fig. 3. Quadrula verrucosa (Rafinesque). Rather large female, from Shenango 

 River, Pulaski, Lawrence Co., Pennsylvania, collected July 19, 1909; C. M. Cat. No. 

 61.4121. 



Fig. 4. Quadrula metanevra (Rafinesque). Normal specimen from Ohio River, 

 Industry, Beaver Co., Pennsylvania, collected September 25, 1908; C. M. Cat. No. 

 61.3865. 



Fig. 5. Quadrula metanevra (Rafinesque). Specimen intergrading toward the var. 

 wardi (Lea), with the tubercles moderately developed and the shell slightly more com- 

 pressed, from Allegheny River, Kelly, Armstrong Co., Pennsylvania, collected September 

 .27, 1907; C. M. Cat. No. 61.3071. 



Fig. 6. Quadrula metanevra (Rafinesque). A rather typical wardi (Lea), strongly 

 compressed and with the large tubercles obliterated, from the Allegheny River, Kelly, 

 Armstrong Co., Pennsylvania, collected August 3, 1908; C. M .Cat. No. 61.3861. 



