CHAP. III.] 
ZOOLOGICAL LEGIONS. 
49 
like starlings to the hang-nests, Ioteridse ; and these four 
peculiar families comprise more than a hundred species, and 
give a special character to the ornithology of the country. 
Add to these such peculiar birds as the mocking thrushes 
(Mimus), the blue jays (Cyanocitta), the tanagers, the peculiar 
genera of cuckoos (Coccygus and Crotophaga), the humming- 
birds, the wild turkeys (Meleagris), and the turkey-buzzards 
(Cathartes), and we see that if there is any doubt as to the 
mammals of North America being sufficiently distinct to justify 
the creation of a separate region, the evidence of the birds 
would alone settle the question. 
The reptiles, and some others of the lower animals, add still 
more to this weight of evidence. The true rattle-snakes 
are highly characteristic, and among the lizards are several 
genera of the peculiar American family the Iguanidse. No- 
where in the world are the tailed batrachians so largely 
developed as in this region, the Sirens and the Amphiumidae 
forming two peculiar families, while there are nine peculiar 
genera of salamanders, and two others allied respectively to 
the Proteus of Europe and the Sieboldia or giant salamander 
of Japan. There are about twenty-nine peculiar genera of 
fresh -w r ater fishes ; while the fresh- water molluscs are more 
numerous than in any other region, more than thirteen hundred 
species and varieties having been described. 
Combining the evidence derived from all these classes of 
animals, we find the Nearctic region to be exceedingly well 
characterised, and to be amply distinct from the Palaearctic. 
The few species that are common to the two are almost all 
arctic, or, at least, northern types, and may be compared with 
those desert forms which occupy the debatable ground between 
the Palaearctic, Ethiopian, and Oriental regions. If, however, 
we compare the number of species which are common to the 
Nearctic and Palsearctic regions with the number common 
to the western and eastern extremities of the latter region, 
we shall find a wonderful difference between the two cases ; 
and if we further call to mind the number of important groups 
characteristic of the one region but absent from the other, we 
shall be obliged to admit that the relation that undoubtedly 
E 
