390 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 



cold wind was blowing at the time. The highest temperature re- 

 corded was 66° F. on July 22, after one of the rare days of full 

 sunshine. 



Mean surface temperature of the water of Aleutian Island 

 pools and lakes, 1937-38 



The fresh-water plankton crustaceans have been identified by 

 Trevor Kincaid, of the University of Washington. His remarks 

 on the material are as follows : 



Very little is known regarding the fresh-water plankton of Alaska, and 

 this is particularly true of the region including the Aleutian Islands which is 

 practically a blank in so far as records are concerned. 



The writer has been assembling plankton from various parts of Alaska 

 with a view to determining the geographic distribution of the species oc- 

 curring in the fresh water bodies in that territory, and to discovering what 

 relation exists between the fauna of Asia and that of Alaska and of North 

 America in general. It is becoming clear that this relationship is much 

 closer than has been suspected. 



In the genus of fresh-water copepods Diaptomus it has been supposed 

 that no species was common to both continents, but we now find several 

 species of this group ranging across Europe and Asia into Alaska, while 

 at least one species having a wide range over western North America has 

 been reported from a lake in Siberia. 



The series of tows brought back by the expedition from the Aleutian Is- 

 lands was regarded as particularly important since the archipelago forms 

 a series of natural stepping stones extending from the Siberian region to 

 the Alaskan Peninsula and southward, and as one might expect to find 

 here the collection extends the known westerly range of several American 

 species, and expands the easterly range of at least one Asiatic form. 



Diaptomxis ashlandi was originally described from Wisconsin and is 

 known to be widely distributed over the northern portion of the Pacific 

 Coast. It appears in tows taken on the islands of Sanak and Unalaska. 

 Diaptomus shoshone var. ivardi was first reported from Spokane, Washing- 

 ton and has since been reported from the Island of St. Paul in the Pribilofs. 

 It appears in a tow taken on Sanak Island. Diaptomus eiseni was described 

 from California, but has since appeared in collections taken at widely sepa- 

 rated localities of the Pacific Coast. It has been reported from a lake in 

 Siberia. A single specimen was found in a tow taken on Sanak Island. 

 Arctodiaptomus kurilensis was recently described from the Kurile Islands 

 by Kiefer. It appears in a tow taken on the islands Kanaga, Tanaga and 

 Atka which lie near the middle of the Aleutian chain. 



The cyclopoid copepods found in the collection are, as might be expected, 

 species already known to be common to both continents, or as in the case of 



