xii PREFACE. 
and conclusions would have nothing solid to rest on), these may 
be omitted by the non-scientific reader, or merely noted as a 
certain number or proportion of peculiar generic types. Many 
English equivalents to family and generic names are, however, 
given; and, assisted by these, it is believed that any reader 
capable of understanding Lyell’s “ Principles,” or Darwin’s 
“ Origin,” will have no difficulty in following the main argu- 
ments and appreciating the chief conclusions arrived at in the 
present work. 
To those who are more interested in facts than in theories, 
the book will serve as a kind of dictionary of the geography 
and affinities of animals. By means of the copious Index, the 
native country, the systematic position, and the numerical 
extent of every important and well established genus of land- 
animal may be at once discovered ;—information now scattered 
through hundreds of volumes. 
In the difficult matters of synonymy, and the orthography of 
generic names, I have been guided rather by general utility 
than by any fixed rules. When I have taken a whole family 
croup from a modern author of repute, I have generally followed 
his nomenclature throughout. In other cases, I use the names 
which are to be found in a majority of modern authors, rather 
than follow the strict rule of priority in adopting some newly 
discovered appellation of early date. In orthography I have 
adopted all such modern emendations as seem coming into 
general use, and which do not lead to inconvenience ; but where 
the alteration is such as to completely change the pronunciation 
and appearance of a well-known word, I have not adopted it. 
T have also thought it best to preserve the initial letter of well- 
known and old-established names, for convenience of reference 
to the Indices of established works. As an example I may refer 
to Enicwrus—a name which has been in use nearly half a 
