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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



insects of restricted food hal)its help? Will gall-forming insects give 

 some light? How about nematodes? Will plant-feeding snails help? 



The last few pages have noted a few sources of data for but one set 

 of problems connected with the biogeography of the Southern Hemi- 

 sphere. There are many other problems and groups of problems. 

 Let us mention only one other. 



It is thought that in Cretaceous times there was a strip of land 

 running north from Japan, Korea and Kamchatka, crossing the 



Fig. 4. — Hypothetical composite map of the Pacific Ocean and adjacent 

 lands during Cretaceous times, showing the land-strip bounding this ocean on 

 the north and east and extending westerly from South America across the 

 southern Pacific to Papua and Australia. Not all parts of this land-strip were 

 in existence at any one time, the northern portions being mostly earlier, the 

 South-Pacific bridge being later, perhaps early Tertiary. (Compiled from 

 several authors, chiefly Arldt.) 



northern Pacific ( )cean and running down the west coast of America 

 to Ecuador and the Galapagos Islands (fig. 4). This circumpacific 

 land strip may have connected at its southwestern end with the 

 northern Malayan region (cf. fig. 2). It is thought to have connected 

 with Eastern Asia in perhaps luimerous places. It may have included 

 the Aleutian Islands or may have lain mostly to the south of them. The 

 mountainous islands of western Alaska, Vancouver Island, the Olympic 

 mountains and the Siskiyou mountains of Northern California were 

 prol)ably included ; so also may have been Mount Tamalpais, the Pre- 

 sidio Hill, the southern California islands, the tip of Lower California 



