424 MESOZOIC TIME — REPTILIAN AGE. 



The Reptiles must have been very diversified in form and size, 

 but, although fragments of the skeletons of several species have 

 been found, a much larger number are known only from their foot- 

 prints. The fossils have been discovered in Prince Edward's 

 Island (Nova Scotia), Pennsylvania, and North Carolina. One of 

 the most interesting localities is at Phoenixville, Pa., where there is 

 literally " a bone-bed," as recently described by Wheatley. Some 

 of the teeth of the Reptiles are shown in figs. 645-648. The ani- 

 mals belonged, apparently, to the tribe of Lacertians (Lizard tribe), 

 and to that of Labyrinthodonts. Fig. 645, from the tooth of a Rep- 

 tile found in Prince Edward's Island {Bathygnathus borealis Leidy) is 

 reduced one-half. 



There may also have been Flying Reptiles, Pterodactyls or species 

 of some other unknown genus of Pterosaurs ; for a fossil found 

 by Wheatley at Phoenixville, Pa., much resembles, according to 

 Leidy, the wing-finger of such a Reptile : it consists of two slender, 

 hollow bones joined by an articulation. None of the footprints 

 correspond in form to the foot of a Pterodactyl ; but it is doubtful 

 whether any tracks of a flying species could reasonably be looked 

 for. 



The Reptilian footprints (figs. 639-644) vary from a length 

 of one-fourth of an inch to twenty inches, and many of them 



with the mouth attached to the nipples; having two hones, called 

 marsupial bones, attached to the anterior margin of the pelvis ; as the 

 Opossum (Didelphys), Kangaroo (Macropus), etc. 

 2. Monotremes. — Without teeth; no external ears; no pouch, but still 

 having marsupial bones: — e.g. (1) the Ornithorhynchus, having a 

 covering of hair and a duck bill; (2) the Echidnus, having a cover- 

 ing of spines and hair, with the habit of the Porcupine. 



This order includes several groups, which are approximately paral- 

 lel with those of the Non-marsupials. 



(1.) Marsupial Monkeys. — Ex., the genus Phalangista (Phalangers), 

 Phascolarctos. 



(2.) Marsupial Carnivores. — Ex., Dasyurus (Bear-Opossum), Thyla- 

 cinus (Dog-faced Opossum), Thylacoleo. 



(3.) Marsupial Herbivores (approximately). — Ex., Hypsiprymnus, 

 Macropus (Kangaroo), Nototherium ; and of the Pachyderm 

 tribe, the great Diprotodon. 



(4.) Marsupial Insectivores. — Ex., Perameles (Bandicoots), Chaero- 

 pus, Myrmecobius, Didelphys (Opossum). 



(5.) Marsupial Rodents. — Ex., Phascolomys (Wombat). 



(6.) Monotreme Edentates. — Ex., Echidnus, Ornithorhynchus. 



The living species are confined to Australia, Tasmania, and the conti- 

 nent of America, one species — the Opossum — occurring in North 

 America, north of the Gulf of Mexico. 



