little article by Maurice Krosby," from which I have copied the attitude, but not the details, of a flying Archæopteryx, it is implied that Archæopteryx had four wings; in fact, it is called Tetrapteryx, a name suggested by Beebe for the hypothetical ancestral bird. Undoubtedly the quills on the legs made a plane of the hind legs, but they were not flapped, while the forelegs or true wings undoubtedly were flapped-the skeleton shows this much.

A comparison, rather remote, it is true, is suggested between the flight of Archæopteryx and that of the modern tinamous of South America, which have somewhat similar short rounded wings. As described by W. H. Hudson, the tinamous fly violently for a maximum distance of perhaps a mile, but usually a much less distance, and then glide to the ground, repeating this two or three times before becoming exhausted. The tinamous are ground dwellers and rapid runners, while Archæopteryx was, on the other hand, clearly a partially arboreal form and scarcely a runner. Its functional clawed fingers must have been habitually used in climbing about in the branches, much as a young hoactzin of South America does and they were also useful in effecting a safe landing in flying from one tree to another or at the end of a glide.

While Archæopteryx may be considered as about 25 per cent. reptilian, it is indubitably a true bird and a long way removed from its scale-covered and cold-blooded reptilian ancestors. There were bipedal bird-like reptiles already present before the close of the Triassic, so that there were some millions of years before the late Jurassic in which to evolve feathers and acquire the art of flying, and we know that the pterodactyls had successfully solved the problem of flight by another method in that same interval.

The present restoration (Fig. 3), which is believed to be far more accurate as to environment and detail than any heretofore attempted, shows the strand of the upper Jurassic mainland with the beach-ridges covered with a low jungle, made up largely of a mixed stand of cycads, with a few tall leathery fronded ferns, together with a scattering of taller conifers, comprising both scale-leafed (Brachyphyllum, Palæocyparis) and broad-leafed (Araucaria) types. High overhead is seen a small long-tailed pterodactyl or winged lizard (Rhamphorhynchus). In the foreground an Archæopteryx is flying. Note the slender body, the short heavily flapped wings, the pelvic plane made by • Popular Science Monthly, Vol. 91, No. 1, 1917. 7 Zoologica, Vol. 2, No. 2, pp. 39-52, 1915.

the widely spaced hind legs with their quill feathers, and the long distichously feathered tail constituting a second plane. At the right another Archæopteryx is shown with a small fish in its sharply toothed beakless jaws. It is perched on the crown of a Zamites of the Williamsonia order of cycadophytes. Note the long tail, the free clawed fingers of the fore limbs firmly grasping the cycad fronds and helping to sustain the long body.

Flying reptiles were evidently much more plentiful than birds during Solnhofen times, judging by the abundance and variety of their remains in these sediments, for nearly 30 different species have been described. They were weird bat-like creatures with pneumatic bones, large eyes, feeble hind limbs, and a keeled sternum for the attachment of the wing muscles like that of a modern flying bird. Their fifth finger had become enormously elongated and strengthened to support the membranous wings, which were thus exactly like the wings of a bat, with this exception, that only one instead of four fingers was elongated.

Ancestral pterodactyls go back at least as far as the Liassic or basal Jurassic. The Solnhofen forms were all relatively small and include over a score of species of the short-tailed Pterodactylus and five species of the long-tailed Rhamphorhynchus. Thus Rhamphorhynchus phyllurus had a total length of about 18 inches, of which two thirds was tail, and a wing spread of about 32 inches. An individual of the latter is shown, high in the air, in the accompanying restoration. Many thousands of years later, just before they became extinct, some of the pterodactyls lost their teeth and acquired bird-like bills and developed to gigantic size. Thus some of the pteranodons from the Upper Cretaceous Niobrara chalk of Kansas had a wing span of 18 feet, which is greater than that of any known bird.

Very many interesting tracks are preserved at Solnhofen, both those made on the emerged and on the submerged mud flats. These range from those of the Solnhofen Limulus or horse-shoe crab to that of an insect trying to extricate itself from the sticky mud, and include many that are problematical in character. One of the most well defined tracks that has been discovered and clearly that of some more or less bipedal vertebrate was early described and named Ichnites lithographica by Oppel. It consists of two rows of four-toed footprints at intervals of about 9 centimeters and about 7 centimeters between those of the right and left foot. Midway between the prints of the right and left foot is a small and shallow furrow of varying width and depth, apparently the trail of a dragging tail.

Alternating with the footprints and midway between them and the tail furrow are elliptical depressions with their long axes directed forward and outward. (This track is shown in Fig. 4.)

FIG. 4. PROBLEMATIC TRAIL, POSSIBLY OF AN IMMATURE Archæopteryx. (After Oppel.)

The question for decision is what sort of an animal made this track and how. Oppel thought that it was made by an Archæopteryx and many have followed him in this interpretation. Any small long-tailed animal with bird-like feet such as birds or some of the contemporaneous bird-like reptiles would readily account for the footprints and tail furrow, but how are the alternating elliptical tracks to be explained. They are too constant and regular not to have been made by the same animal that made the other parts of the trail. It has been commonly supposed that Archæopteryx made the whole trail by using its wings like a pair of crutches, the point of rest being the carpal or wrist joint. This is of course possible. Or it is possible that some other and as yet otherwise unknown animal made the tracks.

The chief objections to their having been made by a mature Archæopteryx are the small size of the footprints-much smaller than the feet of the two known specimens, the fact that the pinnately feathered tail would hardly leave a tail furrow in the mud that would look exactly like this one does, and that the wing quills would hardly permit of the wings being used as crutches. Nor is it easy to understand why the functional fore feet were not used. Moreover, if the weight rested on the wings, as assumed, the extremity would sink deep in the soft mud and hinder rather than help locomotion, as well as ruin the quills for purposes of flight. This would be equally true upon hard ground unless the quills were held in an unnatural way. It would further seem that if this were the true interpretation, the long slender body would demand that the ends of the wings rest farther apart. How the bird managed to hop at all, unless the wing-prints were one or more intervals in front of the corresponding footprints is difficult to understand. It is useless to deny the possibility of the accepted interpretation. I am, however, more inclined to think that while this trail belonged to Archæopteryx, it represents the trail of an immature and as yet practically flightless individual, which progressed in this way when on the ground-their small size might suggest this, and the difficulties about the wing and tail feathers would be obviated by their not having as yet become fully functional in size and possibly only sufficiently grown to permit gliding.

The terrestrial vegetation still remains to be considered briefly. Fossil plants have been known from Solnhofen since the days of Sternberg's "Flora der Vorwelt." In striking contrast to the variety and abundance of the animal remains, the traces of the former vegetation that clothed the near-by land are only occasionally met with in the lithographic stone, and even when present they are for the most part fragmentary.

The reasons for this absence of plants are to be found in the macerating action of the water, the non-deciduous character of the foliage of Jurassic plants, the activity of bacteria in the warm sea water, and most of all to the situation of the deposits, away from any estuary with its stream-borne load of land-derived débris. That these reasons are valid is corroborated by the fact that the few plants that have been discovered are such as have leathery decay-resisting parts such as cone scales and coniferous twigs, thus indicating that all the more delicate plant fragments had been destroyed, and by the additional fact that in other regions at this time where the sediments are more clearly of an estuary type as in the fish beds of