48 THE STORY OF REPTILE LIFE. 



animal to drag its prey under water, and yet 

 save itself from drowning by the inrush of water 

 into the open mouth. In other words, it must 

 drown its prey without drowning itself. To do 

 this the hinder margin of the tongue is raised into 

 a transverse fold, which is met by a similar fold 

 hanging from the back of the roof of the mouth, and 

 known as the velum palatinum. When the edges 

 of these two folds meet, the mouth cavity is com- 

 pletely shut off from the throat, and consequently 

 from the entrance to the gullet and windpipe. 



If we turn to the skull we shall find that besides 

 this peculiar modification of the soft parts of the 

 mouth, other and very considerable changes have 

 taken place in the form and arrangement of those 

 bones of the palate which are concerned in the 

 formation of the respiratory passages. As 

 result of these changes the creature is enabled to 

 lie submerged and open-mouthed, in wait for 

 his prey, the while breathing as freely as if on 

 land. To understand the nature and extent oi 

 this peculiar modification, a brief sketch of the 

 method of conveying the air to the windpipe 

 and lungs in reptiles, unmodified in this respect, 

 will be helpful. In them the nasal passages, 

 traced from the snout backwards, open into tho 

 roof of the mouth near the middle of the palate, 

 the air passing from thence to the aperture of the 

 windpipe at the back of the throat or pharynx^ 

 Now in the Crocodiles these passages are con^ 

 tinued backwards to the extreme hinder end of the 

 skull, so that the air is conveyed from the nasal 

 passages backwards directly into the pharynx, 

 which, as we have already seen, is, by a special 



