Bibliographical Notice. 877 



the Memoir was written. The White River group of Tertiary beds 

 forms the "Mauvaises Terres " on the White (or White Earth) and 

 Niobara Rivers. It is divisible into the (lowest) A. Titanotherium- 

 bed, 100 feet ; B. Oreodon-bed, 100 feet; C. sandy beds, with few 

 fossils, 80 feet ; D, Grit and sand (few fossils), 400 feet ; E. Sand- 

 stone and conglomerate, 200 feet [ A-E = Miocene (?) . Marcou 

 thinks that some of these beds may be Jurassic or Triassic !] ; 

 F. Freshwater limestone, marls and sands, sand with Mastodon 

 and Elephas, altogether 200 feet [PUocene] ; surmounted with 

 Post-pliocene yellow siliceous marl, &c., with extinct and recent 

 Vertebrates and recent MoUusks. A list of the numerous Vertebrata, 

 described by Leidy, from these deposits, was lately given in the 

 'Annals Nat. Hist.' ser. 3. vol. xi. p. 148. The 63 extinct species 

 (20 Rutninantia, 12 Multu7igula, 9 Solidungula, 6 Rodentia, 14 Car- 

 nicora, and 2 Chelonia) are tabulated, with their stratigraphical 

 distribution, at p. 106 of the memoir before us. 



The close physical and organic connexion between the Cretaceous 

 group, No. 5, and the "Estuarine group" induces Messrs. Hayden 

 and Meek to regard the latter as of Eocene age, and as having 

 " ushered in the dawn of the Tertiary epoch " with lakes and estua- 

 ries on the upraised Cretaceous area. "The estuary deposits soon 

 lose their marine and brackish character, and gradually pass up into 

 the true Lignite-strata of purely freshwater origin, thence by a slight 

 discordancy into the Wind River Valley beds, which give evidence of 

 being an intermediate deposit between the true Lignite and the White 

 River Tertiary beds. Then come the White River bone-beds, which 

 pass up into the Pliocene of the Niobara by a slight physical break, 

 and the latter are lost in the Yellow Marl or Loess deposits. I have 

 estimated the entire thickness of Tertiary rocks in the north-west at 

 from 5000 to 6000 feet ; and their interest wUl be appreciated wheu 

 I venture to suggest that by thorough investigation they will doubt- 

 less reveal, step by step, in a most remarkably clear manner the 

 history of the physical growth and development of the central por- 

 tion of this continent" (p. 129). 



The author remarks that in the north-west the Lower Silurian 

 beds indicate shallow water ; that in the Carboniferous epoch com- 

 paratively few deep-water deposits were formed there, arenaceous beds 

 predominating ; that neither the Infrajurassic red sandstones nor 

 the Jurassic shales and sandstones represent deep water; and that only 

 in the middle Cretaceous strata is there much evidence of the preva- 

 lence of " long-continued periods of quiet water," and deep, in these 

 ancient western seas ; and these were succeeded by shallow-water 

 conditions and dry land in Tertiary times, when the fluviatile Mollusca 

 were such as now live in Southern Africa, Asia, China, and Siam, 

 and when Palms, such as now exist in the tropics, flourished on the 

 low land now represented by the Rocky Mountains, which have 

 since formed a barrier to the moist west winds, and thus helped to 

 bring about the comparative sterility of the central plains (p. 131). 



IX. The superficial deposits (p. 107, &c.) comprise, 1st (lowest), 

 the Drift, consisting of sand, pebbly clay, gravel, and boulders, and 



Ann. i^ Mag. N. Hist. Ser. 3. Vol.Td. 25 



