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Hanna — Notes on Pribilof Islands. 



species of diatoms as well as mollusks found therein 

 would be found in the waters round about at the present 

 time. But this is not the case. The common fossil spe- 

 cies are exceedingly rare or entirely absent from the 

 region to-day. Likewise the dominating species to-day, 

 Coscinodiscus aster omplialus has not been found as a 

 fossil. In fact several genera which would be expected 

 such as C am pylo discus, Arachnoidiscus and Aulico discus 

 were not found. 



The violent volcanic disturbance which was required to 

 pile up the mountains of lava has required a considerable 

 period of time (years), for all traces to disappear. But 

 only two slight earthquakes, or signs of volcanic action, 

 have been recorded since 1786 when the group was dis- 

 covered. This together with the fact that a mountain of 

 hard lava more than 1,000 feet high has been more than 

 half eaten away by the sea indicates that the islands in 

 point of years are very old. 



Still there is no evidence that an ice sheet of greater 

 weight than those visiting the shores to-day has ever vis- 

 ited the islands. This makes it seem doubtful if they had 

 cooled at the time of the glacial descent. Few plants and 

 animals have become sufficiently differentiated to receive 

 separate specific names from those of neighboring land; 

 geologically therefore the group must be very young. 



The original size of the Pribilof Islands and the rate 

 of erosion form a subject of interesting speculation. 

 That they were originally very much larger than now can- 

 not be doubted because many mountains and hills facing 

 the sea have been more than half eaten away and slope 

 backward. One important fossil-bearing deposit has dis- 

 appeared within historical times. Unless volcanic dis- 

 turbances come to the rescue they must all eventually be 

 torn down, become reefs for the restless surf to break 

 over, and, at last, cease to exist. 



It should be stated here that the reports of the finding 

 of bones of fossil elephants on the Pribilof Islands are 

 probably attributable to practical jokes which have been 

 played on credulous naturalists in the past. No such 

 bones have thus far been found that were not planted by 

 man, according to reports of eye-witnesses to some of the 

 pranks. 



