THE TRIASSIC PERIOD. 



223 



which is the fact that the animal possessed the power of 

 walking, temporarily at least, on its hind-legs, which were 

 much longer and stronger than the fore -limbs, and which 

 were sometimes furnished with no more than three toes. 

 As the bones and teeth of Deinosaurs have been found in 

 the Triassic deposits of North America, it may be regarded as 

 certain that some of the bipedal tracks originally ascribed to 

 Birds must have really been produced by these Reptiles. It 

 seems at the same time almost a certainty that others of the 

 three-toed impressions of the Connecticut sandstones were in 

 truth produced by Birds, since it is doubtful if the bipedal 

 mode of progression was more than an occasional thing 

 amongst the Deinosaurs, and the greater number of the 

 many known tracks exhibit no impressions of fore - feet. 

 Upon the whole, therefore, we may, with much probability, 

 conclude that the great class of Birds (Aves) was in existence 

 in the Triassic period. If this be so, not only must there 

 have been quite a number of different forms, but some of 

 them must have been of very large size. Thus the largest 

 footprints hitherto discovered in the Connecticut sandstones 

 are 22 inches long and 12 inches wide, with a proportionate 

 length of stride. These measurements indicate a foot four 

 times as large as that of the African Ostrich ; and the animal 

 which produced them — whether a Bird or a Deinosaur — must 

 have been of colossal dimensions. 



Finally, the Trias completes the tale of the great classes of 

 the Vertebrate sub-kingdom by presenting us with remains of 

 the first known of the true Quadrupeds or Mammalia, These 

 are at present only known by their teeth, or, in one instance, 

 by one of the halves of the lower jaw ; and these indicate 

 minute Quadrupeds, which present greater affinities with the 

 little Banded Ant-eater {Myrmecobiiis fasciatus, fig, 158) of 

 Australia than with any other living form. If this conjecture 



Fig. 156. — Lower jaw oi Dromatherium sylvestre. 

 Trias, North Carolina. (After Emmons.) 



Fig. 157. — a. Molar tooth of 

 Microlestes afitiqn7(s, magni- 

 fied ; b. Crown of the same, 

 magnified still further. Trias, 

 Germany. 



be correct, these ancient Mammals belonged to the order of 

 the Marsupials or Pouched Quadrupeds {Marsupialia), which 



