PL.ATE XXIV 



PAGE 



Fig. 1. OSTREA SUBSPATULATA Forbes 561 



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

 Pleasant, Prince George's County. 



Figs. 2-4. OSTREA TECTICOSTA Gabb 560 



2. Interior of left valve. X 2. 



3. Exterior of same. X 2. 



Monmouth formation, Brooks' Estate near Seat Pleasant, 

 Prince George's County. 



4. Double valves from the right side. X 2. Monmouth formation, 



Brightseat, Prince George's County. 



Figs. 5, 6. OSTREA FABA Gardner n. sp 559 



5. Exterior of right valve. 



6. Interior of same. 



Monmouth formation, Brooks' Estate near Seat Pleasant, 

 Prince George's County. 



920 



