340 REPORTS OF BERING SEA COMMISSION. 



Woru rocks. the former movements of the seals. This pol- 

 ishing-, though now partly hidden by ^^-eathering 

 and the growth of lichens, is still conspicuous, 

 and can be attributed to no other cause than to 

 the movements of the seals on the rookeries 

 during a long period of years. The fact that the 

 sides of these same rocks remain in their orio-inal 

 rough condition is, sufficient proof that the 

 smooth upper surfaces could not have been j)ro- 

 duced by sand-polish. 



Buucii- grass In some of the rookeries another zone may be 

 discerned behind the yellow-grass zone, indi- 

 cating the extent of tlie rookery at some still 

 more remote period. The grass on this area is 

 bunch grass (BescJiampsia ccespitosa) ; the lichen 

 growth on the rocks is heavier than on the one just 

 described, and the polished surfaces of the rocks 

 show more weathering. This latter zone abuts 

 ag-ainst the more elevated turf bearin"- the char- 

 acteristic tall grass of the islands, and marks the 

 period of maximum abundance of the seals. 



Comparative '^^^^^ aggregate size of the areas formerly occu- 

 pied is at least four times as great as that of the 

 present rookeries. 



Decrease shown In sliort, the characteristics of a region long 



by rookeries. • i i i i i i 



occupied by seals are so marked as to be unmis- 

 takable, and while it is possible to explain the 

 existence of a small part of the unoccupied 



