No. 380.] DEVONIAN PTYCTODONTIDA. 547 
the anterior margin and boundary of the triturating surface 
very fairly ; much more so than its fellow, just above, which is 
the poorest preserved of all. 
There is really less difference in the form of the lower dental 
Fic. 48.— Paleom wius greenei Newb. Group of four naturally associated dental plates. Teeth 
of the lower jaw at ai and teeth of the upper jaw at bottom of the figure. Those belonging 
to the left side of the mouth are on the left, se those belonging to the right side are on the 
right of the figure. 
plates than might be inferred from the photograph, owing to 
perspective effects due to the curved surface of the left lower 
