322 GEOGRAPHICAL AND GEOLOGICAL DISTRIBUTION. 



five thousand feet. The species, like many of the other Mediter- 

 ranean forms, is found also in Algeria, but seems to be absent from 

 Morocco. 117 All of the German species occur in Switzerland, which, 

 however, numbers one additional form, Tropidonotus viperrinus. 



The Mediterranean fauna, or what might be considered to be 

 the fauna of Southern Europe, comprises about thirty species, in 

 which are included probably all the forms that occur elsewhere in 

 Europe ; the Iberian Peninsula numbers twelve species, 118 Italy about 

 fifteen, and Greece fourteen. 119 In the western half of this region 

 the similarity existing between the ophidian faunas of the several 

 countries amounts almost to identity, but eastward, from the Balkan 

 Peninsula to the Crimea, a gradual exchange of species is effected, 

 so that in both Turkey and Russia nearly, or fully, one-half of the 

 species (about fifteen in each country) are distinct. Somewhat more 

 than one-half of the Italian and Iberian species are also found in 

 the region south of the Mediterranean Algeria and Morocco. 



The North American serpents, or those found north of the 

 Mexican boundary, belong in the main to two families, the colubers 

 (Colubridre) and pit- vipers or rattlesnakes (Crotalidae), the former 

 numbering some one hundred and ten or more species, and the 

 latter about twenty. In addition to these there are a limited num- 

 ber of representatives of three or four other families. Thus, the 

 worm or burrowing snakes (Typhlopidae), whose species are abun- 

 dantly distributed over the tropical regions of both hemispheres, 

 occur sparingly in California and Texas (Stenostoma) ; the Erycida3, 

 a limited family of Old and New World serpents allied to the boas, 

 are represented on the west coast by two species of Charina (Cali- 

 fornia to Puget Sound) ; and the venomous Elapidae, to which very 

 nearly two-thirds of all the Australian snakes', and the deadly cobra 

 (Naja), Bungarus, and Ophiophagus of India belong, are repre- 

 sented by the harlequin-snake (Elaps fulvius) in the Southern United 

 States (east of the Mississippi), and by Elaps euryxanthus in Ari- 

 zona. The greater number of these forms can scarcely be said to 

 constitute a part of the North American ophidian fauna proper, 

 inasmuch as they occur principally in a border tract whose gen- 

 eral faunal relationship is more nearly with the region lying to the 

 south than the north. 



The North American colubrine snakes are comprised principally 

 in five or six groups or genera : 1. Tropidonotus, water-snakes, whose 



