MAMMALIAN RULE. 253 



first attempts of nature. There is nothing transitional about ) 

 them. They bring with them no reminiscences of reptiles, 

 birds, or fishes. If they had descended from humbler forms, 

 it must have been by many generations ; and many connect- 

 ing links must be totally lost. If these facts were an iso- / 

 lated group, we might think these little mammals abruptly 

 ushered into being; but the question receives light from so 

 many directions, that we must at least hesitate to accept 

 that view. 



Whatever the origin of these little fore-runners of a noble 

 type, it can not be supposed they had no companions. There ^ 

 must have been hundreds, if not thousands, of individuals of 

 each of these species, but they are wholly lost to knowledge.^ 

 Where we are sure of the disappearance of so many remains, 

 how easy to believe the remains of different creatures of 

 lower mammals have also disappeared. 



Mammals once in existence, we are compelled to believe 

 that they continued uninterruptedly in existence until our' 

 own times. We can not admit that the type was lost to the 

 world, and then the same identical conception reintroduced. 

 But where did mammals live ; where did they perish ; where 

 lie their bones ? Save one or two thin bone beds, we search 

 in vain the depth and breadth of Jurassic and Cretaceous 

 strata for evidences of the existence of mammals. In a bone- 

 bed of the Stonesfield Slate of the English Jurassic, the teeth 

 and jaws of several species of mammals have been found. 

 These are mostly near relatives of the Triassic mammals. In 

 the Middle Purbeck of the Upper Jurassic, occur other remains. 

 We know in Europe, all together, not much over fourteen / 

 species, and they are probably all marsupial; and a majority 

 are insectivores. In the Jurassic of America, Professor Marsh 

 has brought to light at least 17 species ; and these all closely / 

 resemble the Old World remains. In all the vast thickness of 

 the Cretaceous strata, but a single species is known, and of 

 this so far as I am informed, but a single individual, and this 

 very imperfectly preserved. It comes from Dakota, and was 

 described in 1884 by Professor Cope, who bestowed on it the 



