Page:Popular Science Monthly Volume 13.djvu/749

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BIRD OR REPTILE—WHICH?

On the same sands at Hastings there have been found large impressions of the three-toed foot of some biped, the length of whose stride was so great that it is impossible not to conclude that they were made by the hind-feet of one or other of the seventy monsters whose bones have been found scattered about within the narrow area of what was once the banks and delta of a great Wealden river, and which, like the giant-lizards, probably walked occasionally, if not always, on their hind limbs with their fore-feet elevated in front. The question again arises, nor is it easy to answer, whether these forms should be called reptilian birds or avian reptiles.

In the northern gallery of the British Museum there is a very instructive specimen of a reptile, the frilled lizard of Australia, caught near Port Nelson while perching on the stem of a tree. Its long tail recalls at once the same appendage in the kangaroos, inasmuch as by its position in the stuffed specimen the creature would seem to use it as a support to its body. Its fore feet are much smaller than its hind, and an Australian resident, to whom the specimen was shown in presence of Dr. Günther and himself—so Dr. Woodward tells in a paper read before the Geological Society remarked—that it not merely sits up occasionally, but habitually runs on the ground on its hind-legs without allowing its fore-paws to touch the earth. The edges of its jawbones are elevated into enamel-tipped denticulations, which remind us of those in the jawbone of the Sheppey fossil. In the same slates which have given us the long-tailed reptilian bird and the long-necked, birdlike lizard, there has been found a three-toed bipedal track which "reminded me," said Dr. Woodward, "at once of what the frilled lizard or the compsognathus might produce under favorable conditions. The slab presents a median track formed by the tail drawn along on the ground; the two hind-feet with outspread toes leave their mark, while the forepaws just touch the ground, leaving a dot-like impression on either side of the median line. The median track is alternately stronger and fainter. Since the tail of the archæopteryx is bordered all the way by feathers, it will at once be seen that it could not leave behind a clean, simple furrow, but a broad smudge composed of many lines, while the tail of a lizard, progressing by hops and supporting itself on its hind limbs and tail, would produce just such an impression.

There is yet another interesting group of extinct forms to which we would refer shortly, termed "winged reptiles, or flying dragons." In the Woodwardian Museum, at Cambridge, there is a large collection of these bones, belonging to many species, from the soft marl in the neighborhood of that town, about which there have been entertained the most diverse opinions by the most eminent naturalists. They have been variously held to belong to bats, to forms between birds and mammals, to reptiles, and even to dolphins. Prof. Huxley finds in them great resemblances to birds; Prof. Owen thinks that they are reptilian remains; while Prof. Seeley, judging from the form of the cranium, is