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574 PROCEEDINGS OF THE NATIONAL MUSEUM 



in determining brackishness in absence of other data. In the Cape 

 Thompson lagoons of very low salinity, the common freshwater 

 calanoid genera of the region, Heterocope and Diaptmnus, have not 

 established populations. A few specimens of D. arcticus were found 

 in one lagoon in August 1960, but since none were collected at other 

 dates, we believe them to be stragglers washed into the lagoon from 

 a freshwater soiu-ce. The few harpacticoid copepod genera that were 

 collected are, like the calanoid genera Eurytemora and Limnocalanus, 

 those having species with varying degrees of euryhalinity— Z)ameZs- 

 senia, Nitocra, Onychocamptus. 



Distribution of Cape Thompson Eurytemora 



The group of eight species of Eurytemora in the relatively small area 

 surveyed on the coast of the Chukchi Sea, ranging 39 miles north and 

 south of Cape Thompson (from latitude 68°15'-67°55' N. and longi- 

 tude 165°02'-166°0S' W.) and about 11 miles inland (from latitude 

 68°11'-68°14' N.) is the largest assemblage of species of the genus 

 recorded from any similar-sized area of the world. This group also 

 represents about one-half of the species known for the world and 

 nearly all of those known for Alaska (8:10) or North America (8:11). 

 Similar large numbers of species occur in coastal areas south of Cape 

 Thompson, where Heron (1964) found, in a single sample, five species 

 in Kivalina Lagoon and four species in two samples from Krusenstern 

 Lagoon. Including those of neritic waters and continental bodies of 

 water, five species are currently known (Hteratm-e and Wilson col- 

 lection) along the Beaufort seacoast from Point Barrow eastwards 

 as well as along the coast of the Bering Sea south to the Alaska 

 Peninsula. Similar numbers occm* in nearby Asian waters so that 

 the geographic region of northern and western Alaska and north- 

 eastern Asia is, in present-day distribution, richer in numbers of species 

 than any other of the world. This large representation probably 

 reflects the northern origin of both the genus and many of its species, 

 and emphasizes how well the biological requirements of the species 

 are met by the arctic-subarctic en\Tronment. The species of all 

 types of habitat illustrate the strong zoogeographic affinity between 

 the copepod faunas of Alaska and northeastern Asia, previously 

 pointed out by M. S. Wilson (1953b). 



The eight species of Cape Thompson Eurytemora include all but 

 one of the total number known for landlocked bodies of water of 

 the Arctic Slope physiographic province of Alaska, of which the 

 Cape Thompson region is a part. In this province, comprising the 

 Arctic coastal plain and the foothills of the Brooks Mountain Range, 



