CROCODILIANS, LIZARDS, AND SNAKES. 1211 



^ion; but several genera occur in one or the other of its districts whidi 

 do not o(;cur elsewiiere. Similarly, no genus of birds or maniinals can 

 l»(» exclusively assigned to its entire area; but Cltamcvu of the former 

 (lass and Haplodontia of the latter are restricted to particular portions 

 of it. 



The Toltecan auhrrginn is characterized by the genera it lacks as well 

 as those which it iwssesses. Thus, it lacks all the genera of Sauria 

 above cited as characteristic of the Sonoran subregion, including those 

 enumerated as])assingover into the Austrorii)arian excei)t Phryuosoma. 

 It also lacks the following genera of snakes which are fcmnd in the 

 Sonoran : 



Liehannra. Ghilomeniseus. 



Pityophis. Zamenis, 



Ophiholu.s. Phyllorhynclms. 



From the Aiistroriparian subregion it differs in the lack of all the 

 numerous genera of fishes and IJatrachia Urodela, which characterize 

 it, excepting only Spelerpes. It lacks also the following genera of 

 snakes; Cyclpphis, Virginia^ HaUlea, ixwd Carphophiops; and A^a/>-/.r is 

 very sparsely if at all represented. 



In its i)ositive characters the Toltecan subregion combines certain 

 forms of both the Sonoran and Austroriparian subregions. Of the 

 former character are Spca, Phrynosoma,, Barissia, Gerrhonatus, Hypsitj- 

 Icna, and Salradora; of the latter kind, iSj)elerpes, Liolepi.sma, Osceola, 

 Storeria, and iSistrurus. Characteristic of Medicolumbia generally: 

 Anihlystoma, Rana, Sceloporus, Eumeees, Diadophis, JSutwnia, Grotalus. 

 Peculiar genera. 



Siredon. Conopsis. 



Thorins. Epif/lottopliis. 



Malachylodes. Ophry((cvs. 



Neotropical genera: (Ediptis, Anolis, Gelestns, AtractuH, Ninia, Dry- 

 mobius, Bothriechis. 



I. TIIK EASTERN SUBREGION. 



The fauna of Batracliia and Keptilia of this subregion is characterized 

 by what it lacks as much as by what it possesses. The numbei* of 

 species which occupy its entire extent exclusively of other subregions 

 is small, while a larger number are restricted to parts of it. Verrill 

 divided it into four distri<*-ts, namely, the Caroliman, the Alleghenian, 

 the Canadian, and the Hudsonian. These are distinguished by the 

 ranges of mammals and reptiles, and the bree(ling-[)laces of birds. The 

 Carolinian fauna extends in a belt north of the Austroriparian subre- 

 gion from Long Island, south of the hill region of New Jersey, to the 

 southeastern (;orner of Pennsylvania, and thence inland. It embraces 

 a wide belt in Maryland and Virginia, and all of central North Carolina, 

 and then narrows very much in passing round south of the Alleghenies 



