593 



The Quaternary fauna of Maine indicates a much more purely arctic assem- 

 blage than is at present to be found.* This is also the rase with the Scandi- 

 navian Quaternary fauna, according to the researches of the late Prof M. 

 Sars As we have before shown, in the essay just referred to, the circum- 

 polar marine fauna extends down along the coast of Northeastern America 

 and of Europe, and the forms common to the two shores are circumpolar 

 forms, members of the circumpolar zoological realm. Europe, in all proba- 

 bility, did not borrow any of her specific forms from America; but both have 

 been, in part, peopled from a purely circumpolar lamia. If there has been 

 any borrowing, it has been on the part of Europe, since the fossil musk- 

 sheep (Ovibos) of France and Central Europe is said to be identical with 

 the musk-sheep of arctic America. So, also, on the coast of Northeastern 

 Asia and Alaska are circumpolar forms, which have evidently been borne by 

 arctic currents down each coast. The forms which are identical or repre- 

 sentative on those two coasts are species derived from the circumpolar fauna : 

 so the forms which are so strikingly similar in Northern Japan to those on 

 the coast of New England are, if we mistake not, also derived from the 

 northward. From the consideration of these facts, we are led to accept the 

 conclusion that congeneric forms occurring on the Pacific slope of North 

 America, as well as Europe and Asia, are the remnants of a southward migra- 

 tion from polar lands during Tertiary times, ami, in proportion to the high 

 antiquity of the migrations, there have been changes and extinctions, causing 

 the present anomalies in the distribution of organized beings which arc now 

 so difficult to account for on any other hypothesis. For this reason, it is not 

 improbable that those species of insects. which are more or less cosmopolite 

 (and independently so of human agency) arc the most ancient, just as some 

 forms taxonomically the most remote are remnants of earlier geological 

 periods. For example, the curious anomalies in the geographical distribution 

 of Limulus, the genus only occurring on the eastern coasts of Asia and 

 North America, accord with its isolation from other Crustacea. Geological 

 extinction has gone hand in hand with geographical isolation. It was not an 

 uncommon form in Europe in the Jurassic period, and was preceded by other 

 Meiostomata in the Palaeozoic periods. 



* "Glacial Phenomena of Labrador and Maine," by A. S. Packard, .jr., in Memoirs of Boston Society 



of Natural History, i, 1865. 



75 p H 



