1921] NATURAL SCIENCES OF PHILADELPHIA. 37 



washed out from the land into the brackish or salt waters and thus 

 given the worm a chance for attachment. You will notice that 

 with the coiled shells there are little ostracodes which are also in- 

 dicative of brackish water conditions. It would be perfectly orderlj- 

 to find this specimen in continental sediments." 



Explanation of Plates I-III. 



Plate I. — Figs. 1-17. Various forms of fish scales. 

 Figs. IS, 19. Coprolite, exterior and section. 



Plate II. — Fig. 1. Diplodon pennsylvanicus n. sp. Type. 



Fig. 2. Diplodon pennsylvanicus. Dorsal view of an obliquely compressed 



specimen. 

 Fig. 3. Diplodon pennsylvanicus. Interior of another specimen. 

 Figs. 4, 5. Diplodon carolus-simpsoni n. sp. Type, dorsal and lateral 



views. 

 Fig. 6. Diplodon carolus-simpsoni. Lateral view of a larger specimen, in 



red shale. 



Plate III. — Fig. 1. Mycetopoda diluculi n. sp. Type, lateral view. 



Figs. 2, 2a. Diplodon yorkensis n. sp. Type, dorsal and lateral views. 



Fig. 3. Spirorbis inexpectatus n. sp. Type and paratypes. 



Fig. 4. Diplodon pennsylvanicus n. sp. 



Fig. 5. Diplodon wanneri n. sp. Type, lateral view. 



