ell, and at the same time became lighter in colour. Just as the
doctor was about to investigate one of them with his duck-shot, the
enormously inflated tops of the creatures collapsed with a loud report,
and the entire group soared away. When about to alight, forty yards
off, they distended membranous folds in the manner of wings, which
checked their descent, and on touching the ground remained where they
were without rebound.

"We expected to find all kinds of reptiles and birds," exclaimed the
doctor. "But I do not know how we should class those creatures. They
seem to have pneumatic feet and legs, for their motion was certainly
not produced like that of frogs."

When the party came up with them the heads again began to swell.

"I will perforate the air-chamber of one," said Col. Bearwarden,
withdrawing the explosive cartridge from the barrel of his rifle and
substituting one with a solid ball. "This will doubtless disable one
so that we can examine it."

Just as they were about to rise, he shot the largest through the neck.
All but the wounded one, soared off, while Bearwarden, Ayrault, and
Cortlandt approached to examine it more closely.

"You see," said Cortlandt, "this vertebrate--for that is as definitely
as we can yet describe it--forces a great pressure of air into its head
and neck, which, by the action of valves, it must allow to rush into
its very rudimentary lower extremities, distending them with such
violence that the body is shot upward and forward. You may have
noticed the tightly inflated portion underneath as they left the
ground."

While speaking he had moved rather near, when suddenly a partially
concealed mouth opened, showing the unmistakable tongue and fangs of a
serpent. It emitted a hissing sound, and the small eyes gleamed
maliciously.

"Do you believe it is a poisonous species?" asked Ayrault.

"I suspect it is," replied the doctor; "for, though it is doubtless
able to leap with great accuracy upon its prey, we saw it took some
time to recharge the upper air-chamber, so that, were it not armed with
poison glands, it would fall an easy victim to its more powerful and
swifter contemporaries, and would soon become extinct."

"As it will be unable to spring for some time," said Bearwarden, "we
might as well save it the disappointment of trying," and, snapping the
used shell from his rifle, he fired an explosive ball into the reptile,
whereupon about half the body disappeared, w