187 
1877) says tliat^ the lowest tertiary beds in the country a 
rich mammalian fauna suddenly makes its appearance/’ The 
lowest tertiary beds are the Eocene. It was the Eocene and 
the lowest of the Eocene beds that yielded the remains of the 
fourteen -toed orohippus and eohippus. If^ then_, this rich 
mammalian fauna, which suddenly appeared, and orohippus 
and eohippus were not fresh creations, but evolutions, where 
do we look for their line of ancestors ? (See Chart on previous 
page.) 
57. The next stratum that we come to is the enormously thick 
cretaceous, consisting of the chalk, the upper green sand, the 
gault, and the lower green sand. I think I may say without 
the fear of contradiction that throughout the length, and 
breadth, and depth of the rocks of the Cretaceous age, no land 
mammals of any kind have ever been found in any part of the 
world. 
58. Professor Marsh makes a similar statement, and says, 
that this is especially to be regretted, as it is evidently to the 
Cretaceous that we must look for the fossil representations of 
any of our present groups of mammals as well as for indica- 
tions of their more ancient lineage.’^ But, however it may be 
regretted, there is the fact before us. Deposits of enormous 
thickness which had taken thousands upon thousands of years 
to form, have never yielded to the geologist a single tooth or 
bone of any kind of mammal; where, then, are we to look for the 
common ancestor of the bear and the horse, and for the 
ancestors of the ri<;h fauna of the Eocene ? Through the 
whole series of descending rocks (after passing the Cretaceous) 
down to the Laurentian, the only mammalian forms known to 
the palaeontologist are those in the Rhaetic beds of Somerset 
(represented by a single tooth), in the Stonesfield slates of 
Oxfordshire, and the Purbeck beds of Swanage. These are the 
only forms known in the Old World, the largest is about 
the size of a full-grown rat. 
59. But it is to the New World that we are directed for the 
earliest ancestor of the horse. And it was of the New World 
that Professor Marsh was speaking when he said, that a 
rich mammalian fauna suddenly made its appearance.^’ What 
about the pre-Eocene Mammalia of America? I will again 
quote Professor Marsh, who says that ^^a single small marsu- 
pial from the Trias is the only mammal found in all the 
American rocks below the Eocene.” 
60. Dr. Darwin’s hypothesis demands a long line of diver- 
sified forms, evolved by minute successive slight modifications. 
From the Trias to the Eocene no mammal of any kind is found 
in the New World nor in the Old World from the Eocene to 
