backward; for it is not pointed, like those of the front toes, but is blunt.  It is true that there is a division of joints in the toes, which seems in favor of the idea that they were those of Birds; for when the three toes are turned forward, there are two joints on the inner one, three on the middle, and four on the outer one, as in Birds.  But this feature is not peculiar to Birds; it is found in Turtles also.  The correspondence of these footprints with each other leaves no doubt that they were all by one kind of animal; for both the bipedal and the quadrupedal tracks have the same character.  The only quadrupedal animals now known to us which walk on two legs are the Kangaroos.  They raise themselves on their hind legs, using the front ones to bring their food to their mouth.  They leap with the hind legs, sometimes bringing down their front feet to steady themselves after the spring, and making use also of their tails, to balance the body after leaping.  In these tracks we find traces of a tail between the feet.  I do not bring this forward as any evidence that these animals were allied to Kangaroos, since I believe that nothing is more injurious in science than assumptions which do not rest on a broad basis of facts; but I wish only to show that these tracks recall other animals besides Birds, with which they have been universally associated.  And seeing, as we do, that so many of the early types prophesy future forms, it seems not improbable that they may have belonged to animals which combined with reptilian characters some birdlike features, and also some features of the earliest and lowest group of Mammalia, the Marsupials.  To sum up my opinion respecting these footmarks, I believe that they were made by animals of a prophetic type, belonging to the class of Reptiles, and exhibiting many synthetic characters.

The more closely we study past creations, the more impressive and significant do the synthetic types, presenting features of the higher classes under the guise of the lower ones, become.  They hold the promise of the future.  As the opening overture of an opera contains all the musical elements to be therein developed, so this living prelude of the Creative work comprises all the organic elements to be successively developed in the course of time.  When Cuvier first saw the teeth of a Wealden Reptile, he pronounced them to be those of a Rhinoceros, so mammalian were they in their character.  So, when Sommering first saw the remains of a Jurassic Pterodactyl, he pronounced them to be those of a Bird.  These mistakes were not due to a superficial judgment in men who knew Nature so well, but to this prophetic character in the early types themselves, in which features were united never known to exist together in our days.

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