FLYING DRAGONS. 131 
they breathe passes, not into their lungs only, but penetrates to 
the remotest parts of their system, filling their very bones with 
life, and endowing them with activity and animation adapted to 
their active aérial existence. It may, therefore, be argued that 
Pterodactyls breathed much in the same way; that their bones, 
too, were supplied with air by an elaborate system of air-sacs, 
and that they had lungs lke those of birds. We cannot, how- 
ever, stop there, but are led on by physiological reasoning to 
conclude that the circulation of the blood must have been rapid, 
and that the heart was like that of birds and mammals, four- 
celled. It would therefore follow—since birds and mammals are 
warm-blooded 
that Pterodactyls were also. Such, at least, is 
the view of Professor H. G. Seeley, who says of the Cambridge 
specimens, ‘‘That they lived exclusively upon land and in air 
is improbable, considering the circumstances under which their 
remains are found. It is likely that they haunted the sea-shores, 
and, while sometimes rowing themselves over the water with their 
powerful wings, used the wing-membranes, as the bat does, to 
enclose their prey, and bring it to the mouth. 
“The large Cambridge Pterodactyls probably pursued a more 
substantial prey than dragon-flies. Their teeth are well suited 
for fish, but probably fowl and small mammals, and even fruits, 
made a variety in their food. As lord of the cliff, it may be 
presumed to have taken toll of all animals that could be 
conquered with tooth and nail. From its brain it might be re- 
garded as an intelligentanimal. The jaws present indications of 
having been sheathed with a horny covering.” 
Probably the large Pterodactyls of the Cretaceous period, 
soaring like albatrosses and giant petrels over the surface of the 
ocean, co-operated with the marine reptiles, such as Ichthyosaurs, 
Plesiosaurs, crocodiles, and others, as those sea-birds now do with 
the whales, porpoises, and dolphins, in reducing the excessive 
numbers of the teeming tribes of fishes, and in maintaining the 
balance of oceanic life. 
