PLATE XIX 



PAGE 



Figs. 1-4. NUCULA SLACKIAXA Gabb 511 



1. Exterior of left valve. 



2. Ventral view of double valves. 



3. Dorsal view of double valves. 



4. Dorsal view of right valve. X 2. 



Monmouth formation, 1 mile west of Friendly, Prince George's 

 County. 



Figs. 5, 6. NUCULA AMICA Gardner n. sp 514 



5. Interior of right valve. X 3. 



6. Exterior of same. X 3. 



Monmouth formation, 1 mile west of Friendly, Prince George's 

 County. 



Fig. 7. NUCULA MICROSTRIATA Gardner n. sp 515 



Exterior of right valve. X 3. Monmouth formation, Brightseat, 

 Prince George's County. 



Figs. 8, 9. LEDA ROSTRATRUNCATA Gardner n. sp 517 



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



near Seat Pleasant, Prince George's County. 



9. Exterior of left valve. X 2. Monmouth formation, 1 mile west of 



Friendly, Prince George's County. 



Figs. 10-12. LEDA WHITFIELDI Gardner n. sp 516 



10. Exterior of left valve. X 4. 



11. Interior of same. X 4. 



Monmouth formation, Friendly, Prince George's County. 



12. Dorsal view of double valves. X 5. Monmouth formation, Bright- 



seat, Prince George's County. 



Fig. 13. YOLDIA LONGIFRONS (Conrad) Johnson 518 



Exterior of left valve. Ripley formation, Union County, Mississippi, 

 U. S. National Museum. 



Fig. 14. YOLDIA NOXONTOWNEXSIS Gardner n. sp 521 



Cast of right valve. Manasquan formation, South Feeder Noxontown 

 Pond, Delaware. 



Fig. 15. NEMODON STANTOXI Gardner n. sp 527 



Exterior of right valve. Monmouth formation, Brightseat, Prince 

 George's County. 



915 



