xIvi INTRODUCTION. 
and gigantic species of the same genera or families of 
Marsupialia :—and that the modern Sloths, Armadillos, and 
Anteaters, chose the route to South America, where only, 
and in the warmer parts of North America, are to be 
found the fossil remains of extinct species of those very 
peculiar edentate genera. It is not less striking and sug- 
gestive, though at first sight less subversive of the recent- 
dispersion theory, to find the Macacus, Elephant, Rhino- 
ceros, Hippopotamus, Hyena, Beaver, Pika, Hare and 
Rabbit, Vole and Mole still restricted to that great natural 
division of dry land, the old world of geography, to which 
the fossil remains of the same genera or species appear 
to be peculiar. These generalizations, and the special facts 
which are treated of in the following pages, must be in- 
terpreted agreeably with right reason, and not warped to 
suit with preconceived views. 
Portion of right upper maxillary bone with the penultimate true molar of a 
fossil Monkey (Macacus pliocenus) ; from the newer pliocene brick-earth at 
Grays, Essex. 1, front view ; a, base of malar process. 2, back view ; >, smooth 
surface of the antrum maxillare. 3, grinding surface of the fossil tooth. 4, grind- 
ing surface of the corresponding tooth of a recent Monkey ( Macacus sinicus). 
