PLATE XXII 



PAGE 



Figs. 1-3. PTERIA RHOMBIC A Gardner n. sp 549 



1. Exterior of right valve of young individual. 



2. Exterior of left valve of adult. 



3. Interior of same. 



Monmouth formation, Brightseat, Prince George's County. 



Fig. 4. OSTREA LARVA SUBS?. FALCATA Morton 552 



Exterior of right valve. X 2. Monmouth formation, Brooks' Estate 

 near Seat Pleasant, Prince George's County. 



Fig. 5. OSTREA LARVA SUBSP. XASUTA Morton 554 



Exterior of right valve. X 1M>- Monmouth formation, Brightseat, 

 Prince George's County. 



Figs. 6-8. OSTREA LARVA SUBSP. MESENTERICA Morton 555 



6. Exterior of left valve. X 4. 



7. Interior of same. X 4. 



Monmouth formation, McNey's Corners, Prince George's 

 County. 



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



near Seat Pleasant, Prince George's County. 



918 



