60 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 54. 



It will be seen from the above that while collections have been 

 made from widely scattered representative locahties in the eastern 

 half of the State, the greater part of my own collections are from an 

 area with the city of Boulder as its center, including 7 lakes on the 

 plains east of this city and 106 in the mountain region to the west. 

 This mountain area I will refer to as the Tolland region after the 

 town of Tolland, where, during most of my study, I made my headquar- 

 ters, at the summer mountain laboratory of the University of Colo- 



KlLOMETERS 



Fig. 1. — Map of Colorado suowing localities where Entomostraca have been collected. The 



BLA.CK rectangle INCLOSES THE TOLLAND REGION, THE AREA SHOWN IN DETAIL IN FIG. 2. 



rado. The lakes of the Tolland and Boulder regions afford especially 

 favorable conditions for the study of altitudinal distribution, because 

 here, within a distance of less than 30 miles, is passed through the 

 whole range of cUmatic conditions, from temperate to subarctic. 

 To the east of Boulder extend the plains with elevations up to 5,400 

 feet, while to the west, clearly visible, 20 miles away, Arapahoe 

 Peak with its glacier, rising to 13,506 feet, marks the Continental 

 Divide. 



The climatological data presented in the following paragraphs, 

 while in general true for any part of the State, apply particularly 

 to this area. 



CLIMATE. 



The data regarding climate presented in this paper are, for the most 

 part, from the annual summaries of the Weather Bureau for the Colo- 

 rado section, though use is also made of data collected by Francis 



