PUZZLES IN PAL.EONTOLOGY. 223 



Other marvellous reptiles lived and died in the Mesozoic 

 period. The Theriodoiitia were powerful and ferocious beasts of 

 prey, with teeth of the carnivorous type. The Anoniodontia had 

 beaks encased in horn, after the fashion of modern turtles. The 

 Ichthyosaurus and Plesiosaurus are types of two orders, compris- 

 ing great fish-like reptiles, or " sea-lizards." Both have but a short 

 geological existence ; they appear in the lias and disappear in the 

 succeeding chalk. There were also the Pterosaurs, which were, 

 in relation to other reptiles, what the bat is compared to other 

 mammals. 



Modern reptiles, like the insectivorous mammals of Europe, are 

 poor and humble survivals of a numerous and powerful race. In 

 England the great " dragons of the prime" are represented but by 

 such small and harmless amphibia as the frogs and newts ; and the 

 crocodiles of the Nile, and the alligators of Florida, are them- 

 selves hardly more than newts compared to that greatest of earthly 

 giants, Atlantosauriis. Amongst the most inexplicable problems 

 of palaeontology are the laws, at present undiscovered, which led to 

 the extinction of these huge reptiles. In the Ui)per Trias appeared 

 some small and feeble mammals, of about the size of mice. Who 

 could have guessed that these small, frail creatures were the ances- 

 tors of the future lords and masters of the world ; that the gigantic 

 and highly-organised Deinosaurs, the terrible '"Sea-Lizards, "and the 

 fierce Theriodontia, would all die out, and that the descendants of 

 these small creatures — these milk-givers with warm blood- -would 

 survive them ? Vvhat but a law governing the duration of species 

 could have destroyed these huge reptiles? Rivals, capable of 

 harming them, did not exist. ^Vhat happened between the laying 

 down of the Cretaceous rocks and the succeeding Eozoic period, 

 during which the small mammals (of marsupial and insectivorous 

 affinities), which first appeared in the Upper Triassic and Jurassic 

 rocks, expanded into countless herds, representing every natural 

 order of mammals of the present day ? And the giant reptiles 

 are all things of the past ! 



In the beds of Upper Jurassic age, on the western slope of 

 the Rocky Mountains, Professor Marsh has found the remains of 

 several hundred mammals. Here, at the dawn of mammalian 

 life, we already meet with three distinct orders, all so far special- 



