I hasten to the conclusion of my sketch. This reptileproducing age of the world was fruitful in the varied forms of gigantic lizards and crocodiles. To the former belong Durydorus serridens, and probably Sauropus primævus of the New Red Sandstone of Pennsylvania, and Bathygnathus borealis (as before stated) of similar rocks in Nova Scotia. The crocodiles of the earlier epoch of the Jurassic Age came upon the earth in herds. They mostly possessed the peculiarity of having their vertebræ concave before and. behind, like those of fishes-a character for which the term amphicalian has been invented by Owen. A few, as the Streptospondylus, were exceptional among vertebrates, in having their vertebræ convex before and concave behind (opisthocælian), while the rule among all existing animals of this family is to have the vertebræ concave before and convex behind (procoelian).

The most gigantic of all reptiles that ever crawled over the face of the earth or swam in its waters were those of the family of Dinosaurians, whose elongated and ponderous forms must grace the picture of Oölitic and Wealden scenes. Of these, the Megalosaurus was the advance guard, and measured forty feet in length. The Iguanodon and Pelorosaurus followed in the Wealden epoch, the former of which was sixty feet in length and the latter seventy! Turtles, the highest order of reptiles, made their advent in small numbers toward the close of the Jurassic Age, but never flourished in abundance till after the reign of gigantic saurians. Just as the curtain was falling on the scenes and actors of this wonderful drama of reptilian life, two or three small mammals ran upon the stage, and gave themselves up to extinction barely in time to enable us to say that the highest class of vertebrates added its contribution to the animal variety of that period in which the Alps were accumulating as sediments in the bottom of the sea. We

have honored their memories by bestowing upon them such names as Thylacotherium, Phascolotherium, and Dromatherium, the latter of which was discovered by Professor Emmons in North Carolina, and all of which occupy a low position in their class.

The Cretaceous Age followed the Jurassic, and the Wealden epoch was its first chapter-unless we adopt the late suggestion to annex it to the Jurassic. The herpetology of this epoch has been worked out by that eminent geologist and good man, the late Dr. Mantell. Besides its flying reptiles, and crocodiles, and turtles, here was the jubilee of those enormous saurians just mentioned. The Dinosaurs were characterized by the presence of a medullary cavity in their long bones, as in mammals; by their short-toed feet, like those of the rhinoceros; by their sacrum, composed of five or more vertebræ consolidated, while in all other reptiles it consists of two or less; by the articulating of the lower jaw so as to adapt it for lateral or grinding movements; by the double head of their ribs, and by the elevation of the body from the ground when walking. In all these characters they show an approach toward the class. of mammals. The age of mammals was not yet; but it was prophesied and heralded from afar by these few sentences transcribed upon the bulletin of creation. The length of the femur or thigh-bone of the Iguanodon was, when full grown, more than four feet and a half, while its circumference around the head was fifty inches, and around the smallest part of the bone twenty-five inches. The teeth were obtusely conical and laterally compressed, so as to present a cutting edge, which was serrated, thus resembling the teeth of the Mexican iguana, from which the fossil reptile was named. It was, undoubtedly, eminently terrestrial in its habits, and subsisted by browsing from the trees of the time, as was the habit of the mastodon of a

later period. Twigs of cypresses have been found fossil in its stomach; and Dr. Mantell possessed a jaw in which the teeth had been worn down by trituration of food to half their original length.

With peculiar pleasure I turn now to results of the study of American cretaceous reptiles, which are no less brilliant and no less marvelous than those of Mantell and Owen in the Old World. Thanks to the skill of Dr. Leidy and Professor Cope, both of Philadelphia, the cretaceous beds of New Jersey have been forced to yield up the secrets of their life-history. We now know that while the chalk was accumulating in Europe, the marshes, and jungles, and bayous of the American shores were the scene of as busy and intense a life as swarmed upon the coasts of England, France, or Germany. The Cimoliasaur (Cimoliasaurus magnus, Leidy) and Elasmosaur (Elasmosaurus orientalis, Cope) presented the form of huge sea-serpents from twenty-five to forty feet in length. The body was swollen out to dimensions exceeding those of an ox, and was furnished with a pair of flippers like the whale. The neck and tail were elongated, and in the latter the tail was flattened, and probably used as an oar in sculling. These were carnivorous monsters, and probably made fierce war upon the feeble representatives of the waning dynasty of fishes. The wrecks of the Mosasaur, of another order of reptiles, are strewn along the ancient coast-line from New Jersey to Alabama, where, at Selma and Cahawba, I have seen fragments of their ponderous skeletons protruding from the face of the limestone cliffs cut down by the Alabama River. The turtles of the period contributed a unique variety to the reptile fauna. Not less than twenty-two species have been described from the cretaceous sands of New Jersey. Nine of these were marine "snapping turtles." One of the latter (Euclastes platyops, Cope)

had a head twelve inches in length, indicating a "snapping turtle" of the formidable length of six feet. The power of such an animal may be estimated by comparison with the familiar "snapper" of modern times.

But the most abundant of all the Cretaceous reptiles of the Atlantic coast were Crocodilians. At the time of which we speak they must have literally swarmed along what is now the river-front of Philadelphia. They peopled every pool and lagoon along the cretaceous shore of Pennsylvania. The Deinosaurs, however, were the great feature of the bayou and the estuary. Like their kindred of the Old World, they rivaled in bulk the yet future mammoth and mastodon. "They exceeded these," says Professor Cope, "in their bizarre and portentous aspects; for some have chiefly squatted, some leaped on the hind limbs like the kangaroo, and some stalked on erect legs like the great birds, with small arms hanging uselessly by their sides, and with bony visage surveying land and water from their great elevation.”

One of the most remarkable of these reptiles was the Lælaps (L. aquilunguis, Cope), a carnivorous kangaroo-like. quadruped twenty-three feet in length. It seemed a rude attempt of Nature to realize the notion of a bird in the framework of an alligator. It walked entirely on its hind limbs, or leaped like the kangaroo. "Its toes were long and slender, and probably similar in number and form to those of a bird of prey. They were armed with flattened hooked claws, which measured from ten inches to a foot in length, and, like those of the eagle, were adapted for grabbing and tearing prey. The teeth were adjuncts in this appropriation of animal life; they were curved, knifeshaped, and crimped or serrate on the margin, and adapted like scissors for cutting" (Fig. 75). This was the most formidable land carnivore of the continent, and second to

none of the Old World. It was the Megalosaurus of Amer ica.

Another of the gigantic reptiles which carried on a war of extermination upon the fields destined to be ensanguined by the battles of Trenton and Brandywine was the Hadrosaur (Hadrosaurus Foulki, Leidy). The visitor to the museum of the Academy of Sciences of Philadelphia can not fail to be impressed by the skeleton of one of these monsters mounted in the attitude of browsing from a cycadeous tree. This piece of work is by the eminent restorer of extinct animals, B. Waterhouse Hawkins, Esq., of London, to whose courtesy I am indebted for the photographic view which adorns the opposite page (Fig. 76). The Hadrosaur attained the length of thirty feet. The femur or thighbone was sometimes five feet in

Fig. 75. Tooth of an ancient New Jersey Saurian (Lœlaps aquilunguis), showing two

successors beneath.

length, exceeding by more than a foot the maximum. length of the femur of the Iguanodon of England, the largest of the hitherto known land reptiles. The fore limbs were less than half the length of the hind limbs. The form of the feet and toes shows that they were poorly adapted for swimming. In its habitual attitude it rested, like the kangaroo, upon its enormous hind limbs and tail. With its supple anterior extremities it reached upward to the foliage of the tree destined to afford it food, and drew the branches down within the reach of the grinding jaws. Not unlikely this land-monster walked at times upon its hind feet, while the ponderous tail dragged behind.