Distribution of Moths of the Sub-family Bistonince. 253 



occupied by the Sierra Nevada, Coast Range and other Moun- 

 tain Systems of California, Oregon, Washington and British 

 Columbia. Exactly how far this extended into the Pacific does 

 not affect our investigation. But let there be no misconception, 

 although the connection was much more precarious than that 

 between Eurasia and America to the west of the former, never- 

 theless there was a North Pacific link, possibly not a broad one, 

 but including what is now the Behring Straits. 



This enormous continent was bounded on the South by 

 the great Sub-equatorial marine belt which effectually separated 

 Eurasia and America from the Africano-Brazilian continent 

 on the one hand, and from the Africano-Australian continent 

 on the other. Whether the latter masses were connected to 

 the west of the former is probable, but still doubtful. 



It will thus be evident that North America was completely 

 cut off from what then existed of South America. In fact, 

 the formation of the Isthmus of Panama, and the uplifting of 

 the Sierra Nevada, Cascade and Coast Ranges are two events, 

 geologically speaking, quite recent in occurrence, certainly not 

 taking place earlier than Pliocene times, and then contem- 

 poraneously. Even the Rocky Mountains are of no great age, 

 the oldest portions being of early Tertiary origin. 



Not only did the Northern Continent extend so far, but 

 the climate, whilst varying as might have been expected as 

 one passed from north to south, was remarkably uniform. 

 Identical species in all groups of animals and plants are wide- 

 spread in Miocene (for this is the period that concerns us most) 

 fossiliferous deposits. In Greenland, Spitzbergen, Europe, 

 Siberia and North America, genera such as Liriodendron (the 

 Tulip Trees), Sequoia (Giant Redwoods of California), Sassafras, 

 Torreya, Magnolia and Onoclea (the Sensitive Ferns) occurred 

 as identical species. 



Where now on the earth's surface are we to search for 

 such forms ? W T e find them in isolated localities, in some 

 cases with a distance of half the earth's circumference between 

 them. The noble Sequoia, which once held sway over the 

 whole earth, now present two species, Sequoia sempervirens and 

 S. gigantea, the latter with a feeble hold on a limited area at a 

 height of 6,000 ft. in the mountains of California, and the 

 former of fairly general occurrence on the western coast of 

 temperate North America. Magnolias and the Liriodendrons 

 are restricted to Eastern North America and Eastern Asia ; 

 whilst Sassafras only survives in Atlantic North America. 

 Torreya — a peculiar gymnosperm genus — follows Liriodendron 

 and the same holds true of the Sensitive Fern ( Onoclea sensibilis). 

 Had we not fossil evidence, it would have been difficult indeed 

 to believe that these plants had once been of general dis- 

 tribution ; in the case of herbaceous forms we can only reason 



1917 Aug. 1. 



