344 MEMOIRS OP THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE I. 



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



Fig. L Margaritanamargaritif era (Linnadus). Normal specimen from Indian Run. 

 Rene Mont, Schuylkill Co., Pennsylvania, collected May 4, 1909; C. M. Cat. No.61.4272, 



Fig. 2. Fusconaia subrotunda (Lea). Young specimen of typical shape, diameter 

 64 per cent of length, from Allegheny River, Godfrey, Armstrong Co., Pennsylvania, 

 collected October 5, 1908; C. M. Cat. No. 6L3941a. 



Fig. 3. Fusconaia subrotunda kirtlandiana (Lea). Old female, diameter 45 per 

 cent of length, slightly drawn out posteriorly, from Allegheny River, Kelly, Armstrong 

 Co., Pennsylvania, collected August 5, 1913.; C. M. Cat. No. 61.6462. 



Fig. 4. Fusconaia subrotunda kirtlandiana (Lea). Typical young specimen, dia- 

 meter 45 per cent of length. May be regarded as a topotype, from Mahoning River, 

 Mahoningtown, Lawrence Co., Pennsylvania, collected August 4, 1908; C. M. Cat. 

 No. 61.3921. 



Fig. 5. Fusconaia subrotunda kirtlandiana (Lea). Adult specimen representing 

 the typical phase, diameter 42 per cent of length, also topotype from Mahoning River, 

 Mahoningtown, Lawrence Co., Pennsylvania, collected October 15, 1908; C. M. Cat. 

 No. 61.3928. 



