Reeth External nostril. 
BELODON 
GAVIAL es, 
_....External nostril. 
.......Eye socket. 
Lye socket. 
BELODON 
= 
Palatine. 2... € + 
__. Posterior or internal nostril. 
Posterior nostril. - 
NEW NOSES FORE®OLD. 
The above illustrations show how the modern Crocodiles and their kin acquired the mechanism which enables them to breathe 
under water while drowning their prey. In the extinct Belodon the external nostrils, it will be seen, open at the base of the 
snout, inithe Crocodiles and Gavials they open atits tip. In Belodon the passage of the nostrils opened into the mouth by passing 
straight: downwards from the upper surface. Here they were guarded on either side by plates of bone forming ledges: these were 
the Palatines. 
In course of time these ledges met in the middle line, involving a similar meeting on the part of the bones next 
behind them—the Pterygoids. 
Finally, the Palatines and Pterygoids from forming an open channel formed a closed tube opening 
at the extreme base‘of the skull, as in the False Gavial and all other kinds of Crocodiles to-day. 
