348 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE III. 



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



Fig. L Amblema plicata costata (Rafinesque) . Typical, gravid female, of good 

 size, representing the compressed creek-form, from Pymatuning Creek, Pymatuning 

 Township, Mercer Co., Pennsylvania, collected July 8, 1909; C. M. Cat. No. 6L4340. 



Fig. 2. Amblema plicata costata (Rafinesque). Exceptional specimen, without 

 oblique undulations, also distinctly more swollen than the normal form, from the Alle- 

 gheny River, KeUy, Armstrong Co., Pennsylvania, collected August 3, 1908; C. M. Cat. 

 No. 61.3829. 



Fig. 3. Amblema plicata costata (Rafinesque). Young specimen with undulations 

 nearly obUterated, also somewhat swollen, from Ohio River, Cook's Ferry, Beaver Co., 

 Pennsylvania, collected October 8, 1909; C. M. Cat. No. 61.4428. 



Fig. 4. Quadrula pustulosa (Lea). Specimen with few tubercles, from the Mahon- 

 ing River, Edinburg, Lawrence Co., Pennsylvania, collected September 15, 1908; C. M. 

 Cat. No. 61.3875. 



Fig. 5. Quadrula pustulosa (Lea). Specimen with numerous tubercles, from Ohio 

 River, Industry, Beaver Co., Pennsylvania, collected October 22, 1908; C. M. Cat. 

 No. 61.3878. 



Fig. 6. Quadrula pustulosa schoocraftensis (Lea). Old female, unusually trans- 

 verse, from Lake Erie, Presque Isle Bay, Erie, Erie Co., Pennsylvania, collected July 8, 

 1910; C. M. Cat. No. 61.4515 



Fig. 7. Quadrula pustulosa schoolcraftensis (Lea). Female of medium size and 

 rather normal shape, from Lake Erie, Cedar Point, Erie Co., Ohio, collected by Chas. 

 Brookover, August 1909; C. M. Cat. No. 61.4451. 



