40 UNIVERSITY OF COLORADO STUDIES 



From east to west the state may be divided roughly into three 

 topographical areas, (i) The eastern two-fifths (approximately) is 

 included in the western portion of the Central Great Plains of North 

 America. It is a region of flat or rolling prairies, semi-arid and tree- 

 less, except along the borders of the few streams, and where artificial 

 irrigation has been adopted. (2) At their western edge the plains 

 abruptly give way to the steep and high foothills which flank the 

 great mass of mountains occupying the central area and extending 

 from the northern border of the state clear across to the southern 

 boundary, enclosing several open areas called "parks," of which the 

 principal ones are North Park, Middle Park, and South Park. (3) The 

 western portion of the state, beyond the higher ranges of mountains, 

 is an area of mesas and dissected plateaus. The foothills and moun- 

 tains are to a great extent heavily forested, chiefly by coniferous trees, 

 up to an altitude of from 10,500 to 11,500 feet. The higher portions 

 of the western mesa region are also forested , chiefly with pinyon pine 

 and cedar. 



Living Faunas and Floras. — In such a region, with its great differ- 

 ences of altitude, temperature, moisture and soil, a large fauna and 

 flora would be expected, and in case of the flora and some of the 

 zoological groups this expectation is fully realized. On the other hand, 

 however, the reptilian and amphibian faunas are not very large, 

 because of certain limiting factors, though there are probably more 

 species found than is popularly supposed. The present paper records 

 altogether 45 species of reptiles and n species of amphibians. 



The class Reptilia includes crocodiles, alligators, turtles, tortoises, 

 lizards and snakes, of which the first two are not found in our area. 

 The class Amphibia (or Batrachia) includes frogs, toads, newts and 

 salamanders. Both classes are included among the so-called cold- 

 blooded animals. Birds and mammals, whose blood is always warm 

 and does not vary much in temperature with changes in the tempera- 

 ture of the surrounding atmosphere, are called warm-blooded animals, 

 and ordinarily to them a change of a few degrees in blood temperature 

 means death. Reptiles, amphibians and fishes are commonly called 

 cold-blooded animals, not because their blood is always cold, but 



