PLATE XXIII 



PAGE 



Figs. 1, 2. OSTREA LARVA SUBSP. MESEXTERiCA Morton 555 



1. Interior of left valve. X I 1 /?. 



2. Exterior of same. X 1V. 



Monmouth formation, Brightseat, Prince George's County. 



Fig. 3. OSTREA SUBSPATULATA Forbes 561 



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

 Pleasant, Prince George's County. 



Ficjs. 4, 5. OSTREA MOXMOUTHENSIS Weller 558 



4. Interior of right valve. 



5. Exterior of same. 



Monmouth formation, Brooks' Estate near Seat Pleasant, 

 Prince George's County. 



919 



