THE REIGN OF REPTILES. 189 



have honored their memories by bestowing upon them such 

 names as Thylacotherium, JPhascolotherium, and Dromathe- 

 o'ium, the latter of which was discovered by Professor Em- 

 mons in North Carolina, and all of which occupy a low po- 

 sition in their class. 



The Cretaceous Age followed the Jurassic, and the Weald- 

 en 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 geolo- 

 gist 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, com- 

 posed of five or more vertebras 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 circumfer- 

 ence 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 resem- 

 bling the teeth of the Mexican iguana, from which the fos- 

 sil reptile was named. It was, undoubtedly, eminently ter- 

 restrial in its habits, and subsisted by browsing from the 

 trees of the time, as was the habit of the mastodon of a 



