"A monstrous bat!" I suggested.

"Nothing of the sort," said the Professor, severely. "Living, as
I do, in an educated and scientific atmosphere, I could not have
conceived that the first principles of zoology were so little known.
Is it possible that you do not know the elementary fact in
comparative anatomy, that the wing of a bird is really the
forearm, while the wing of a bat consists of three elongated
fingers with membranes between? Now, in this case, the bone is
certainly not the forearm, and you can see for yourself that this
is a single membrane hanging upon a single bone, and therefore
that it cannot belong to a bat. But if it is neither bird nor
bat, what is it?"

My small stock of knowledge was exhausted.

"I really do not know," said I.

He opened the standard work to which he had already referred me.

"Here," said he, pointing to the picture of an extraordinary
flying monster, "is an excellent reproduction of the dimorphodon,
or pterodactyl, a flying reptile of the Jurassic period. On the
next page is a diagram of the mechanism of its wing. Kindly compare
it with the specimen in your hand."

A wave of amazement passed over me as I looked. I was convinced.
There could be no getting away from it. The cumulative proof
was overwhelming. The sketch, the photographs, the narrative, and
now the actual specimen--the evidence was complete. I said so--I