378 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE XVIII. 



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



Fig. 1. Lampsilis ovata (Say). Normal adult male from the Allegheny River, 

 Kelly, Armstrong Co., Pennsylvania, collected August 30, 1907; C. M. Cat. No. 6L2994. 



Fig. 2. Lampsilis ovata (Say). Normal gravid female from the Allegheny River, 

 Kelly, Armstrong Co., Pennsylvania, collected August 30, 1907; C. M. Cat. No. 61.2994. 



Fig. 3. Lampsilis ovata (Say). Male, strongly inclining in shape toward the var. 

 ventricosa, from the Allegheny River, Kelly, Armstrong Co., Pennsylvania, collected 

 July 5, 1909; C. M. Cat. No. 61.4007. 



Fig. 4. Lampsilis ovata ventricosa (Barnes). Male, slightly inclining toward the 

 normal ovata, from French Creek, Cambridge Springs, Crawford Co., Pennsylvania, 

 collected September 13, 1909; C. M. Cat. No. 61.3996. 



