346 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE II. 



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



Fig. 1. Fusconaia fiava trigona (Lea). Typical specimen of this form, diameter 

 66 per cent of length, from Monongahela River, Charleroi, Washington Co., Pennsyl- 

 vania, collected by G. A. Ehrmann; C. M. Cat. No. 6L58696. 



Fig. 2. Fusconaia flava parvula Grier. Male, from the type-set, diameter 52 per 

 cent of length, from Lake Erie, Presque Isle Bay, Erie, Erie Co., Pennsylvania, collected 

 July 8, 1910; C. M. Cat. No. 61.4513. 



Fig. 3. Fusconaia flava (Rafinesque). Typical specimen, diameter 42 per cent of 

 length, from Raccoon Creek, New Sheffield, Beaver Co., Pennsylvania, collected October 

 11, 1907; C. M. Cat. No. 61.3151. 



Fig. 4. Amblema plicata (Say). Old full-grown specimen of the typical plicata 

 from the type-locality. Lake Erie, Presque Isle Bay, Erie, Erie Co., Pennsylvania, col- 

 lected June 3, 1908; C. M. Cat. No. 61.3336. 



Fig. 5. Amblema plicata (Say). Young specimen, topotype, from Lake Erie, 

 Presque Isle Bay, Erie, Erie Co., Pennsylvania, collected July 8, 1910; C. M. Cat. No. 

 61.4518. 



Fig. 6. Amblema plicata (Say). Specimen of medium size, unusually compressed, 

 topotype from Lake Erie, Presque Isle Bay, Erie, Erie Co., Pennsylvania, collected 

 July 8, 1910; C. M. Cat. No. 61.4518. 



Fig. 7. Amblema plicata costata (Rafinesque). Rather young specimen of the 

 much compressed form of the small creeks, from French Creek, Cambridge Springs, 

 Crawford Co., Pennsylvania, collected September 13, 1909; C. M. Cat. No. 61.4348. 



