168 
GEOGRAPHICAL ZOOLOGY. 
[PART IV. 
There is also a considerable difference in the dependence to be 
placed on the details given in the different classes of animals. 
In Mammalia and Birds some degree of accuracy has, it is hoped, 
been attained; the classification of these groups being much 
advanced, and the materials for their study ample. In Eeptiles 
this is not the case, as there is no recently published work 
dealing with the whole subject, or with either of the larger 
orders. An immense number of new species and new genera of 
snakes and lizards, have been described in the last twenty years ; 
and Dr. Gunther — our greatest authority on reptiles in this 
country — has kindly assisted me in incorporating such of these 
as are most trustworthy, in a general system ; but until entire 
Orders have been described or catalogued on a uniform plan, 
nothing more than a general approximation to the truth can be 
arrived at. Still, so many of the groups are well defined, and 
have a clearly limited distribution, that some interesting and 
valuable comparisons may be made. 
Bor Dishes, the valuable “ Catalogue ” of Dr. Gunther was 
available, and it has rarely been attempted to go beyond it. A 
large number of new species have since been described, in all 
parts of the world ; but it is impossible to say how many of 
these are really new, or what genera they actually belong to. 
The part devoted to this Class is, therefore, practically a summary 
of Dr. Gunther’s Catalogue ; and it is believed that the dis- 
coveries since made will not materially invalidate the conclusions 
to be drawn from such a large number of species, which have 
been critically examined and classified on a uniform system by 
one of our most able naturalists. When a supplement to this 
catalogue is issued, it will be easier to make the necessary altera- 
tions in distribution, than if a mass of untrustworthy materials 
had been mixed up with it. 
For Insects, excellent materials are furnished, in the Catalogue 
of Mr. Kirby for Butterflies and in that of Drs. Gemminger and 
Harold for Coleoptera. I have also made use of some recently 
published memoirs on the Insects of Japan and St. Helena, and 
a few other recent works ; and have, I believe, elaborated a more 
extensive series of facts to illustrate the distribution of insects, 
