PLATE XXVII 



PAGE 



Figs. 1, 2. EXOGYRA COSTATA Say 564 



1. Exterior of right valve. Monmouth formation, Brightseat, Prince 



George's County. 



2. Exterior of left valve. Monmouth formation, Brooks' Estate near 



Seat Pleasant, Prince George's County. 



Fig. 3. EXOGYRA COSTATA SUESP. CAXCELLATA Stephenson 566 



Exterior of loft valve. Monmouth formation, head of Little Bohemia 

 Creek, Cecil County. 



923 



