324 HENRY B. ward; 



One of the earliest investigations on elevated lake regions 

 and the only one yet made in this country is that of Forbes (93) 

 in Wyoming and Montana. Noteworthy is the careful study 

 of the entire environment and its influence on the fauna. In 

 this Forbes made valuable contributions to the general char- 

 acter of the fauna of elevated lakes which were utilized by 

 Zschokke in the paper already noted. Among the features 

 discussed by Forbes are the extreme poverty of the vertebrate 

 aquatic fauna, the ruling species being rather Amphipods, leeches 

 and insect larvae, great rarity of mollusks, the abundance of 

 Entomostraca, largely cosmopolitan species, and the sharp 

 eontrasl of the fauna in adjacent water basins. There exists 

 a deepwater fauna in many of these lakes, of which something 

 was asc srtained. In general the fauna proved to be richer 

 than that of Lakes at corresponding and even less elevation in 

 Europe. The influence of environment was well shown by 

 variations in the fauna, such as the abundance of mollusks in 

 a lake lying within a lime formation and their rarity in all 

 other elevated waters. 



Only one investigator has yel endeavored to group into re- 

 gions in accordance with their fauna, the lakes of any conti- 

 nental area. Zograf (96) divides the lakes of Russia into four 

 regl d upon the distribution of the fish and crustaceans. 



The first region includes the large water basins in the north- 

 in portion of Russia, the second surrounds the first, the 

 third includes the lakes of Central Russia and is little known, 

 and the fourth takes in the steppe lakes bordering upon the 

 south. Geological evidence supports this general classifica- 

 tion, the first three being in territory covered by glacial sheets 

 in different periods and the last constitutes the remains of a 

 miocene sea covering southern Russia. 



In discussing the distribution of the fauna within a single 

 body of water authors have regularly adopted Forel's lacus- 

 trine regions and the majority have also made use of the 

 terms introduced by Pavesi to designate the plankton organ- 

 is, ns as eulimnetic or regular inhabitants of the open lake and 

 'limnetic or chance members of the same region. The 



