424 MESOZOIC TIME REPTILIAN AGE. 



The Reptiles must heave 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 Phcenixville, 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 Phcenixville, 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 bones, called 

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

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

 2. Monotremes. — Without teeth j 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 Tnseetivores. — Ex., Perameles (Bandicoots), Chasro- 

 pus, Myrmecobius, Dirlelphys (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. 



