178 E. M. Kindle — Diatomaceous Dust. 



coast that diatoms resort to the under surface of the ice in 

 abundance and are able to live there. 



The abundance of diatoms in all of the samples of dirt col- 

 lected from the Bering Sea ice suggests that the normal habitat 

 of some of the species obtained for part of the year is the shal- 

 low ponds of fresh or brackish water on the ice cakes. One of 

 the pools from the margin of which diatom-bearing dirt was 

 obtained is shown in the photograph, fig. 1. Some of the 

 species may attach themselves to the under surface of the ice 

 as observed by Vanhoffen in the early winter while it is thin, 

 become frozen in and reach the upper surface by the melting 

 of the upper layer of the ice in early summer. 



The siliceous tests of these minute plants comprise an 

 important component of the fine-textured sediments which the 

 annual melting of the Bering Sea floes is sifting down on the 

 sea bottom. 



The nearest locality to Bering Sea from which diatoms have 

 been found on floe ice is near Cape Wankarema, west of Bering 

 Strait about 200 miles. 



Comparison of the species in the dirt from Bering Sea ice 

 with those collected from the ice floes near Cape Wankarema 

 by Xjellman of the Yega expedition and by Nansen during 

 the drift of the Fram affords some interesting data on the 

 relationship of floras found on the ice in the Arctic Ocean 

 and in the Bering Sea. But one species, Coscinodiscus 

 curvatulus, is common to the Bering Sea diatoms from the ice 

 near Cape Bomanzof, and those collected by Kjellman and 

 JSansen in the Polar basin ; nine species of the Bering Sea ice 

 flora occur in the Pacific south of Bering Sea; two are found 

 in the southern part of Bering Sea ; one, JSTaviada fontinalis, 

 is not recorded from the Pacific by Mann.* 



It is thus seen that the affinity of this ice diatom flora is 

 very decidedly with that of the Pacific flora to the south and 

 not at all with that of the Polar sea. This is especially signifi- 

 cant when it is recalled that the diatom fauna of Cape 

 Wankarema, which is only about 400 miles from Cape 

 Bomanzof, bears the closest resemblance to the diatom fauna of 

 the east coast of Greenland. The identity of the large num- 

 ber of species from the two localities was an important part of 

 the evidence which led Nansen to formulate the theory of ice 

 drift across the Polar basin from the Siberian toward the 

 Greenland coast, which his journey afterwards demonstrated to 

 be true. The two samples of mud collected by Kan sen from 

 the floe ice east of Greenland during his expedition to Green. 



* Albert Mann, Report on the Diatoms of Albatross voyages in the Pacific 

 Ocean, 1888-1904. Contr. from the U. S. Nat. Herbarium, vol. x, pt. 5, 

 pp. 225-419, pis. 44-54. 



