238 



EXTINCT ORDERS OF REPTILES. 



Finally, it may just be mentioned that the remains of 

 Deinosaurs («. ^., Agatliaumas) are found in the so-called 

 " Lignitic Series " of North America, which some high 

 authorities regard as being really of early Tertiary age. The 

 evidence available at present is, however, decidedly in favour 

 of the view that these deposits truly belong to the closing 

 portion of the Cretaceous period. 



Order X. Theriodontia. — This order has been founded 

 by Professor Owen for the reception of a number of carnivor- 

 ous Reptiles from deposits of Triassic or Permian age. The 

 Eeptiles in question show some singular Mammalian affini- 

 ties, especially to the Beasts of Prey. The dentition is of the 

 carnivorous type, the teeth heing in three distinct sets — viz., 

 incisors, canines, and molars, and the canines heing large and 

 pointed. 



In Cynodraco, which may be regarded as the best known 

 form of the group, the canines are not only of immense size, 



Fig. 5S0.— A, Front view of the skull of Lycosanrus, sliowiug the dentition ; b, Front view 

 of the jaws of Cynodraco scrrldms, showing the ineisor teeth ; c, Side view of the jaws of Lyco- 

 saurus, showing the incisors and the laniailform canines, c, Canines. (After Owen.) 



but are compressed in shape, and have the hinder trenchant 

 border of the tooth minutely serrated, thus somewhat resem- 

 bling the canines of the Sabre-toothed Tiger [Machairodiis). 

 The humerus is, further, furnished with a " supra-condyloid 

 foramen" (similar to that of the humerus of the Fclidcc) 



