V 



176 LIFE OF THE PLEISTOCENE 



Bison species (cf. bison). 



Black Hawk County. Bank of Cedar River near La Porte City, vertebrae 

 (Hay, page 316). 



Guthrie County. Bear Grove, molar (Hay, page 316). 



Tilton 196a reports several vertebrates from terrace deposits south of Des 

 Moines which are thot to be of Wisconsin or early post-Wisconsin age. The 

 following species are mentioned: 



Bison (metapodial and astragalus) 

 Mastodon or Elephant (tusk and large bones) 

 Rangijer muscatinensis (vertebra and piece of lower jaw) 

 Symbos cavifrons (atlas) 



E. SOUTH DAKOTA 



Todd 197 records the presence of the mammoth (Elephas columbi) in a high 

 terrace just east of the Big Sioux River, above the falls and opposite the City 

 of Sioux Falls. The deposit is loamy sand, sixty feet above the river. The 

 bones were found six feet beneath the surface of the terrace. 



V. The Champlain Substage 



Following the Algonquin stage, the land was notably depressed and partly 

 submerged by an arm of the sea which filled at least a part of the Ontario 

 basin, extending up the Ottawa Valley past the City of Ottawa, and also 

 occupying the Lake Champlain basin and extending down the Hudson River 

 Valley to meet the sea at New York. It seems evident that the subsidence 

 of the land was rather sudden and the elevation of the land gradual, a condition 

 indicated by the nature and position of the life contained in the deposits, the 

 deep water forms overlying the boulder clay, while the littoral forms are near 

 the top of the strata. Dr. J. W. Dawson has published a section made on 

 Logan's farm which brings out these facts graphically. 198 



Soil and sand 1 ft. 9 in. 



Tough, reddish clay " y 2 " 



Gray sand, with few specimens of Saxicava rugosa ( = arctica) Mytilus edulis, 



Macoma groenlandica, and Mya armaria, the valves generally united " 8 " 



Tough, reddish clay, with few shells of A starte laurentiana and Leda portlandica 1 " 1 ' 



Gray sand, containing detached valves of Saxicava rugosa, Mya truncata, Macoma 



groenlandica, Trichotropis borealis and Balanas crenatus, the shells in 



three thin layers " 8 " 



Sand and clay, with few shells, principally Saxicaia in detached valves 1 " 3 ' 



Band of sandy clay, full of Natica clansa, Trichotropis borealis, Fusus tomatus, 



Buccinum undatum, Astarla laurentiana, Balanus crenatus, etc., sponges and 



!9»a pj. oc Iowa Acad Sci ; XXII, pp. 233-236, 1915. 



197 Bull. No. 1, So. Dakota Geol. Surv., pp. 125-126, Bull. 158, U.S. Geol. Surv., p. 85. 



198 Can. Nat., IV, p. 25. 





