FOSSIL BIRDS. 
355 
singular phase. Astonishing in their vast proportions as are 
the fossil reptiles of the Jurassic ages displayed in gig-antic 
models in the pleasure-grounds of Sydenham;, still more asto- 
nishing are other reptilian relics of those marvellous times. 
Then it was that reptiles flew. Sluggish as are now presented 
to us the cold-blooded crocodile, frog, and turtle, reptiles then 
spread an expanse of leathern wing of sixteen feet, and took, 
perhaps, long and unwearied flights. What lives they led no 
man yet has told. But who can look on their petrified forms, 
and not feel a strange inquisitiveness about their habits ? Were 
they ceaselessly on the wing, like the summer swallow after 
insect-prey ? We tliink not, although there were great insects 
in those days — dragon-flies, beetles, grasshoppers. Hovering 
like hawks, did the little spalacotheria, triconodons, and pla- 
giaulaxes tremble under the dark shadows of their sombre 
wings ? We think not, although the bones of those tiny mam- 
mals swarm in the Purbeck beds. Like the albatross did the 
pterodactyles travel for days together over the watery main ? 
Or, like the sea-eagle, did they swoop down on the placid fish as 
they came to the surface of the briny deep ? We are not aware 
that any one yet has made a guess as to what the Pterodactyles 
fed upon ; but we think it would be worth while to inquire 
whether the numerous cuttle-fish of those ages may not have 
been one source of nutriment. 
In the Gault,' near its junction with the Lower Greensand, 
there is a thin but regular stratum of broken ammonites im- 
pacted in a phosphatic paste, and very probably of coprolitic 
origin. May not this stratum have been derived from the 
excrements of the Wealden Pterodactyles? That they swarmed 
in our British area is evident from the quantities of their bones 
found with the nodules of the Cambridge Greensand ; and if it be 
said that the Upper Greensand is a superior stratum to the 
Wealden beds, it might be urged on the other hand that it 
was probably a deeper sea deposit of contemporaneous age. 
The Iguanodons of the Wealden era are found in the Lower 
Greensand, why should not the Pterodactyles, whose bones 
and debris occur at Cambridge, have floated on their wide- 
expanded wings over the tangled forests of the ancient W eald ? 
It seems at first sight perfectly astonishing how few remains 
of birds have been preserved in a fossil state ; but when the 
fragile pneumatic structure of their bones is taken into account 
the wonderment decreases. Still it does not cease, for we find 
the flying-lizards’ bones preserved, and they are filled with air- 
cavities as are those of birds, although perhaps the bones them- 
selves may be of stouter or more solid build. The true explana- 
tion of the matter seems to be that birds dying on the land were 
exposed uncovered on the ground, not only to the eyes of 
