17 



The Pterosauria, or flying Lizards, are among the most 

 interesting Reptiles of Mesozoic time, and many of them left 

 their remains in the soft sediments of our inland Cretaceous 

 sea. These were veritable Dragons, having a spread of wings 

 of from ten to twenty-five feet. They differed essentially from 

 the smaller Pterodactyls found in the old world, in the entire 

 absence of teeth, showing in this respect a resemblance to 

 modern birds ; and they possess other distinctive characters. 

 They have therefore been placed in a new order, Pteranodontia, 

 from the typical genus Pteranodon, of which five species are 

 known. The only other genus is Nyctosaurus, represented by a 

 single species. All the specimens yet found are from essen- 

 tially the same horizon, in the Chalk of Kansas. The reported 

 discovery of remains of this order from older formations in this 

 country is without foundation. 



The strange Reptiles known as Dinosauria, which, as we 

 have seen, were numerous during the deposition of our Triassic 

 shales and sandstones, have not yet been found in American 

 Jurassic, but were well represented here throughout the Cre- 

 taceous, and at its close became extinct. These animals possess 

 a peculiar interest to the anatomist, since, although reptilian 

 in all their main characters, they show clear affinities with 

 the Birds, and have some features which may point to Mammals. 

 The Cretaceous Dinosaurs were all of large size, and most of 

 them walked on the hind feet alone, like modern Struthious 

 birds. Two well marked types may be distinguished among 

 the remains discovere:! in deposits of this age : the herbiv- 

 orous forms, represented mainly by Hadrosaurus, a near ally of 

 the Iguanodon of Europe ; and their carnivorous enemies, of 

 Which Dryptosaurus (Lcelaps) may be considered typical in this 

 country, and Megalosaurus in Europe. Near the base of our 

 Cretaceous formation, in beds which I regard as the equivalent 

 of the European Wealden, the most gigantic forms of this 

 order yet discovered have recently been brought to light. One 

 of these monsters (Titanosaurus montanus), from Colorado, is 

 by far the largest land animal yet discovered; its dimensions 

 3 



