PLATE XXXI 



PAGE 



Figs. 1-3. GRYPH^A (PYCNODONTE) VESICULABIS (Lamarck) Race D.. .. 576 



1. Exterior of adult left valve. 



2. Interior of right valve. 



3. Interior of left valve of same individual. 



Monmouth formation, Brightseat, Prince George's County. 



927 



