LIFE 665 



whose exact relations to the ice invasions can be fixed are found in 

 the interglacial beds. Of these, the most instructive which have 

 luvn studied carefully in America are those on the Don River and in 

 the Scarboro cliffs, near Toronto. 1 The fossil-bearing beds are 

 underlain by a sheet of bowlder clay older than the late Wisconsin 

 sheet of drift. The upper surface of this underlying till was eroded 

 before the overlying fossiliferous interglacial beds of stratified sand 

 and clay were deposited upon it. After the erosion of the latter, a 

 thick body of drift of Late Wisconsin age was deposited upon it. 



The lower part of these interglacial beds contains fossils of a 

 warm-temperate fauna and flora, while the upper contains the relics 

 of a cold- temperate fauna and flora. Up to 1900, the lower beds 

 had yielded 38 species of plants, many of which indicate a climate 

 appreciably warmer (3 to 5) than that of the same region now. 

 Among these are the pawpaw and the osage orange, which now 

 flourish farther south. The fauna includes about 40 species of 

 mollusks, some of which are now living in Lake Ontario, some in 

 Lake Erie, while some are not known in the waters of the St. Law- 

 rence system. The fossils of the upper beds include 14 species of 

 plants, and 78 species of animals, mostly beetles. This assemblage 

 implies a climate of about the type which now prevails in southern 

 Labrador. The arctic fauna and flora which should have followed 

 this cold-temperate one, marking the approach of the next ice-sheet, 

 are undiscovered. 



In other interglacial formations there is evidence at many 

 points of an ample growth of vegetation, recorded in peat and muck 

 beds, in humus-bearing soils, and in twigs, limbs, trunks, etc., of 

 trees, but from them few species have been identified. Recently, 

 bones of horses (more than one species) have been found in the 

 Aftonian interglacial beds in Iowa, 2 along with bones of elephants 

 and mastodons. 



Marine Life 



On northerly coasts. During that stage of the Wisconsin 

 glaciation when the eskers of Maine were being formed, and the sea- 

 level stood higher than now relative to the land along that part of 



1 Coleman, Interglacial Fossils from the Don Valley, Toronto, Am. Geol.. 

 Vol. XII, 1894, pp. 86-95, with references to earlier literature; also Glacial and 

 Interglacial Beds near Toronto, Jour. Geol., Vol. IX, 1901, pp. 285-310. Professor 

 Coleman thinks (1913) that the Don beds are of Aftonian age. 



2 Calvin, G. S. A., Vol. XX. 



