26 PROGRESS OF PALEONTOLOGY n 



entire orders of animals of the existence of which 

 we should know nothing except for the evidence 

 atVorded by fossil remains. AVith all this it may 

 be safely assumed that, at the present nmin. nt, 

 \\. are not acquainted with a tithe of the fossils 

 which will sooner or later be discovered. If we 

 may judge by the profusion yielded within tli. 

 last few years by the Tertiary formations of North 

 America, there seems to be no limit to the multi- 

 tude of mammalian remains to be expected from 

 that continent; and analogy leads us to expect 

 similar riches in Eastern Asia, whenever the 

 Tertiary formations of that region are as carefully 

 explored. Again, we have, as yet, almost every- 

 thing to learn respecting the terrestrial population 

 of the Mesozoic epoch ; and it seems as if the 

 Western territories of the United States were 

 about to prove as instructive in regard to this 

 point as they have in respect of tertiary life. My 

 friend Professor Marsh informs me that, within 

 two years, remains of more than 160 distinct in- 

 dividuals of mammals, belonging to twenty species 

 and nine genera, have been found in a space not 

 larger than the floor of a good -sized room ; while 

 beds of the same age have yielded 300 reptiles. 

 varying in size from a length of 60 feet or 80 fn-t 

 to the dimensions of a rabbit. 



The task which I have set myself to-night is to 

 endeavour to lay before you, as briefly as possible, 

 a sketch of the successive steps by which our 



