384 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE XXI. 



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



Fig. L Lampsilis orbiculata (Hildreth). Half-grown female from the Allegheny 

 River, Godfrey, Armstrong Co., Pennsylvania, collected October 8, 1908; C. M. Cat. 

 No. 6L3504. 



Fig. 2. Lampsilis orbiculata (Hildreth). Very large and much swollen gravid 

 female from the Ohio River, Industrj^, Beaver Co., Pennsylvania, collected September 23, 

 1908; C. M. Cat. No. 61.3500. 



Fig. 3. Truncilla triquetra Rafinesque. Male from the Allegheny River, Kelly, 

 Armstrong Co., Pennsylvania, collected September 27, 1907; C. M. Cat. No. 61.2985. 



Fig. 4. Truncilla triquetra Rafinesque. Gravid female from the Allegheny River, 

 Kelly, Armstrong Co., Pennsylvania, collected September 27, 1907; C. M. Cat. No. 

 61.2985. 



Fig. 5. Truncilla rangiana (Lea). Adult male from French Creek, Cochranton, 

 Crawford Co., Pennsylvania collected September 2, 1908; C. M. Cat. No. 61.3363. 



Fig. 6. Truncilla rangiana (Lea). Half-grown female from French Creek, Coch- 

 ranton, Crawford Co., Pennsylvania, collected September 2, 1908; C. M. Cat. No. 

 61.3363. 



Fig. 7. Truncilla rangiana (Lea). Fully adult gravid female from French Creek, 

 Cochranton, Crawford Co., Pennsylvania, collected September 2, 1908; C. M. Cat. 

 No. 61.3363. 



