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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 54. 



make it possible to determine if there is a zonation similar to that 

 just described for our own mountains, and a comparison of the greatest 

 recorded elevations for each of the 19 common species, while showing 

 a general agreement, also presents some strikmg differences which 

 make comparisons on this basis of little direct use. The average 

 difference in greatest elevations is approximately 3,500 feet, which 

 probably expresses the relative values of altitude in the two regions 

 as affectmg plankton Crustacea. 



Table 6. — Species common to the three mountain regions. 



Name. 



Holopedium gibberum 



Daphnia longispina 



Daphnia pulex 



Daphnia hyalina 



Simocephalus vetulus 



Ceriodaphnia pulchella 



Ceriodaphnia quadrangula . 

 Scapholeberis mucronata . . , 

 Streblocerus serricaudatus . . 



Macrothrix hirsuticornis 



Bosmina longirostris 



Eurycerus lamellatus 



Acroperus harpae 



A lona affinis 



Alona costata 



Colo- 

 rado 

 Moun- 

 tains. 



Swiss 

 Alps. 



Swed- 

 ish 

 Moun- 

 tains. 



Name. 



Colo- 

 rado 

 Moun- 

 tains. 



Alonaguttata ' * 



Alona quadrangularis \ 



Alonella excisa | * 



A lonella eiigua j * 



Pleuroxus truncatus j 



Chrjdorus spbaericus * 



Cyclops albidus * 



C. bicuspidatus ! * 



C. serrulatus 



C. strenuus 



C. vernalis 



C. viridis 



Diaptomus denticornis 



Canthocamptus minutis... 



Swiss 

 Alps. 



Swed- 

 ish 

 Moun- 

 tains. 



* * 

 * 



* * 

 * 



* * 



* * 



* * 



* * 



* 



Ekman (1905), in an extensive account of the plankton Crustacea 

 of the high mountains of northern Sweden, lists 49 species, 15 of 

 which are also in the Colorado mountain list and 19 of them in 

 Zschokke's list from the Alps. In the three mountain lists there 

 are 12 common species, certainly a strikingly large duplication 

 considering the wide separation of the areas. Ekman recognizes 

 three zones, birch, willow, and lichen, which he makes the basis of 

 faunal zones. The limits and characters are shown in Table 7, 

 compiled from his data. 



Table 7. — Table of zonation in Swedish mountains. 



Above 1,350 meters depressions are filled with permanent snow. No fauna. 



In determining the character of the entomostracan fauna of a lake, 

 Ekman considers that temperature is of prime importance. He 

 finds that in all zones the smaller bodies of water open earher in the 



