130 EXTINCT MONSTERS. 
the existence of Pterodactyls during that period fully equal in 
size. ; 
But the largest Pterodactyls hail, like so many other big 
things, from America. Professor Marsh tells us of monsters in 
his famous collection with a spread of wings of twenty to twenty- 
five feet! These large forms had no teeth in their jaws, and 
their skulls are of a peculiar form. ‘The long-pointed jaws were 
probably sheathed in horn during life, as in birds (see Fig. 36). 
According to Marsh, these toothless forms (which he calls 
Pteranodonts) were mostly of gigantic size. With regard to their 
food it is almost vain to speculate; but if they dd prey upon 
fishes, they must have had a capacious mouth and gullet, and 
must have swallowed their prey whole, after the fashion of pelicans. 
But we doubt if they had the peculiar pouch possessed by those 
birds. In the absence of more complete accounts of the large 
forms the artist has only attempted to restore the small ones. 
(See Plate XII., showing four different kinds.) 
Whether Pterodactyls were cold-blooded or warm-blooded is 
a question on which the authorities are not agreed. Professor 
Owen argued from the absence of feathers that they could 
not have been warm-blooded. But, in spite of this great 
authority, who has defended his opinion somewhat strongly, 
there are others who argue that the amount of work involved in 
sustaining a Pterodactyl in the air make it highly probable that 
it was warm-blooded. ‘The absence of feathers to retain the heat 
of the body need not be regarded as conclusive, for bats are 
warm-blooded animals, and in their case the heat of the body is 
retained by a slight downy covering to the skin. Such a covering 
may have protected the bodies of Pterodactyls, and we could not 
expect to see any trace of it in the Bavarian specimen of 
Rhamphorhynchus referred to above. An important fact bearing 
on this question is the discovery of perforations in the bones of 
these animals very similar to those seen in birds. Now, birds 
have a wonderful system of respiration, or breathing. ‘The air 
