342 



THE PORTLAND OOLITE PERIOD. 



CHAP. 



and from the fourteenth they diminish continually, as we proceed 

 backward, till at the twentieth they become sensibly smaller than 



Diagram CXXXIV. Upper jaw of Pleiosaurus brachydeirus. One-tenth of nature. 



in the fore-part of the jaw. The sockets are separated by thin 

 septa, and are ranged in a broad groove, about three feet in length, 



