CLIMATIC CHANGES 89 



with Macoma fusca, which indicate a cUmate like that of the pres- 

 ent St. Lawrence valley. The occurrence of relict colonies of 

 Ostrea virginiana var. horealis and Venus mcrcenaria at various 

 places in the maritime provinces, and in shell heaps along the New 

 England coast as far as Casco Bay, Maine, indicates a period of 

 warmer climate than the present, since these species are now limited 

 in their northward migration by Cape Cod. The extinction of this, 

 and the character of the present fauna indicate a return to cooler 

 conditions. Warmer water conditions inland are also indicated by 

 the occurrence of Unios and other fresh-water molluscs in the 

 gravels of Goat Island and the banks near the Falls of Niagara, 

 some of which (Unio clavus, U. occidcns, and U. solidus and the 

 Margaritana) live to-day only in tributaries of the Mississippi to the 

 south. Evidence of change of climate during Pliocenic times in 

 Japan is indicated by the succession of molluscan faunas (Yoko- 

 yama-iio). From beds regarded as of middle Pliocenic age. a 

 molluscan and brachiopod fauna of decidedly boreal character has 

 been obtained. In the Upper Pliocenic near Tokyo was obtained 

 a molluscan fauna less boreal in character, though indicating still 

 colder conditions than exist at the present time. Still higher beds, 

 referred to the Pleistocenic (Diluvial), contain a molluscan and 

 coral fauna, many species of which are now found only in much 

 more southern localities, the China Sea, the Philippines, and the 

 tropical portions of the Pacific and Indian oceans. If the identifica- 

 tions of these formations as Pliocenic and Pleistocenic, respectively, 

 are correct, the remarkable conclusion would have to be drawn that 

 Japan actually had a warmer climate than to-day, while Europe and 

 America were suffering glacial conditions. In order to bring Japan 

 into harmony with the western world, we would have to assume 

 that the deposits called Pliocenic on the basis of numerical pre- 

 ponderance of living species are actually later in age, i. c, are all 

 Pleistocenic. Such an assumption is not unwarranted. 



The Pliocenic or Crag faunas of England show a progressive 

 refrigeration of the climate. The mollusca of the lowest of these, 

 the Coralline Crag, still bears the stamp of a more genial climate 

 than the present, in spite of the admixture of a few boreal types. In 

 the next division, the Red Crag, the number of boreal species in- 

 creases so as to form 10%, while the succeeding Norwich Crag 

 has a still greater percentage of northern forms. Finally, the high- 

 est, the Chillesford and Wegbourne Crags, have a really boreal or 

 arctic molluscan fauna, including Tcll'ma baltica, Soxicava arctica, 

 Mya arenaria, M. truucata, Cyprina islaudica. Astarfc compressa, 

 A. sulcata, A. borealis, Turritclla tcrebra, Trophon antiquus, Pur^ 



