494 GEOLOGY. 



of material. The formation is but scantily accessible except as arti- 

 ficially exposed. The wood found seems to be largely coniferous, 

 apparently white cedar {Thuya occidentalis) . Sphagnum moss has 

 been identified by Ma^Bride. 



The Yarmouth horizon between the Kansan and Illinoian glacial 

 beds has yielded relics of the wood rabbit (Lepus sylvaticus) and of 

 the skunk (Mephitis mephitica). 1 Peat, containing twigs, and humus- 

 bearing soils indicate a prevalent vegetation. To the Sangamon 

 horizon has been referred coniferous wood, the common peat moss, 

 Hypnum aduncum, and, doubtfully, Elephas primigenius. The Peoria 

 horizon carries peat accumulations. Between the two Wisconsin 

 stages of glaciation no important organic accumulations are known. 



Marine life on the more northerly coasts. — During that stage of the 

 late Wisconsin glaciation when the eskers of Maine were being formed, 

 and the sea-level stood higher than now relative to the land in that 

 part of the coast, arctic mollusks abounded in the shore waters and 

 were buried in marine clays formed contemporaneously with the 

 eskers. 2 From these marine beds, Packard has identified above a 

 score of mollusks, among which are species of Saxicava, Leda, Astarte, 

 Yoldia, My a, and several other genera. The species have a northerly 

 range, and live in waters that are near the freezing-point most of the 

 year. There have been found also remains of walruses, seals, and 

 whales. 



In the Champlain sub-stage, the last episode of the Pleistocene or 

 the opening episode of the Recent period, the arms of the sea that 

 occupied the lower St. Lawrence and Champlain valleys were peopled 

 by an ample marine fauna of essentially the same type as that which 

 now lives about the mouth of the St. Lawrence and on the coast of 

 Labrador. Some signs of progress in numbers and variety in the 

 course of the sub-epoch are suggested by the fact that the higher 

 beds are more fossiliferous than the lower ones. Two sub-faunas 

 have been recognized, that of the Leda clays below, and that of the 

 Saxacava sands above, but it is not j^et quite clear how far this dis- 

 tinction represents a prevalent chronological succession, and how far 

 it is but a local adaptation to conditions of depth and bottom. The 



'McGee, 11th A. Rep. U. S. Geol. Surv. Leverett, ' Mon. XXXVIII, U. & 

 Geol. Surv., p. 42, 1899. 



2 Stone, Mon. U. S. Geol. Surv., XXXIV, 1899, pp. 53-54. 



