132 ORGANIC EVOLUTION CONSIDERED 



The above is a remarkable state of facts if the 

 numerous kinds of large and highly-organized 

 placental mammals which are found in the Eocene, 

 immediately succeeding the Cretaceous, were evolved 

 from Cretaceous marsupials. 



During the immense time of the Cretaceous, while 

 38,000 feet of rocks were being deposited, the mar- 

 supials and monotremes of the Jurassic did not be- 

 come placental mammals, and, we may add to this the 

 6,000 feet of Jurassic and 15,000 feet of Triassic, 

 — making the whole Mesozoic 59,000 feet thick — and 

 during this enormous time small marsupials remained 

 such, so that at the close of the Cretaceous, so far as 

 fossils show, both large marsupials and placental 

 mammals were absent. 



If, as Geikie says, " the great abundance and per- 

 fect preservation of the reptilian forms in these 

 rocks " would cause us to expect the remains of 

 mammals in them, then we ought to expect the 

 remains of large and small placental mammals and 

 of the transitional forms between them and the mar- 

 supials. This, at least, is one of the very special 

 cases where, if evolution has taken place, we have 

 the right to believe that the record would have been 

 preserved, and its absence inay be strongly urged 

 against the truth of that theory. 



We have but to consider the Eocene mammals and 

 contrast them with the small marsupials of the upper- 

 most Cretaceous in order that we may see the force of 

 the above statement. As to the Tertiary marsupials, 

 Dana says : 



"The Marsupials, as in earlier time, were small 

 species, related to the Opossums, and their remains 

 are known from the Early Eocene onward." * 



" No immediate precursors of the Tertiary non- 



*. Manual of Geology, p. 902. 



