The seven genera italicized have a decided preponderance of Nearctic species, and have every right to be considered typically Nearctic; while the remainder are so well represented by peculiar species, that it is quite possible many of them may have originated here, rather than in the Palæarctic region, all alike being quite foreign to the Neotropical. On the whole, then, we have 47 in the first and 7 in the second table, making 54 genera which we may fairly class as typically Nearctic, out of a total of 168 genera of land-birds, or nearly one-third of the whole. This is an amount of peculiarity which is comparable with that of either of the less isolated regions; and, combined with the more marked and more exclusively peculiar forms in the other orders of vertebrates, fully establishes Temperate North America as a region, distinct alike from the Neotropical and the Palæarctic. _Reptiles._--Although temperate climates are always comparatively poor in reptiles, a considerable number of genera are peculiar to the Nearctic region. Of snakes, there are, _Conophis_, _Chilomeniscus_, _Pituophis_, and _Ischnognathus_, belonging to the Colubridæ; _Farancia_, and _Dimodes_, Homalopsidæ; _Lichanotus_, one of the Pythonidæ; _Cenchris_, _Crotalophorus_, _Uropsophorus_, and _Crotalus_, belonging to the Crotalidæ or rattlesnakes. Of Lizards, _Chirotes_, forming a peculiar family; _Ophisaurus_, {120}the curious glass-snake, belonging to the Zonuridæ; with _Phrynosoma_ (commonly called horned toads), _Callisaurus_, _Uta_, _Euphryne_, _Uma_, and _Holbrookia_, genera of Iguanidæ. Testudinidæ, or Tortoises, show a great development of the genus _Emys_; with _Aromochelys_ and _Chelydra_ as peculiar genera. _Amphibia._--In this class the Nearctic region is very rich, possessing representatives of nine of the families, of which two are peculiar to the region, and there are no less than fifteen peculiar genera. _Siren_ forms the family Sirenidæ; _Menobranchus_ belongs to the Proteidæ; _Amphiuma_ is the only representative of the Amphiumidæ; there are nine peculiar genera of Salamandridæ. Among the tail-less batrachians (frogs and toads) we have _Scaphiopus_, belonging to the Alytidæ; _Pseudacris_ to the Hylidæ; and _Acris_ to the Polypedatidæ.