AMERICA. 131 



tract consists chiefly of crystalline rocks, covered in places by Drift 

 and alluvial beds, and resembling the Laurentian of Canada. It -is in 

 these crystalline metamorphic rocks that the iron-ores occur, in lines^ 

 ranges y or belts. Between rock free from magnetite and the richest ore 

 there is a perfect passage. The granitic rocks that contain magnetite 

 generally cut the beds of gneiss, and are huge ore-bearing dykes. 

 Being contemporaneous with the gneissoid rocks, the ore-beds have 

 been subject to the? disturbing forces that have affected them. W. "W. 



Stevenson, Prof. John J. Heport on the Geology of a Portion of 

 Colorado examined in 1873. Rep. Geol. Surv. W. of 100th Me- 

 lidian, part iv. vol. iii. Geology, pp. 20, 307-508, 10 woodcuts. 



Chaps. XI. Metamorphic Eocks, pp. ,343-355. XII. Palajozoic 

 Hocks : Silurian and Carboniferous, 356-^377. XIII. Mesozoic Rocks : 

 Triassic, Jurassic, Cretaceous, Age of the Colorado Lignites, 378-410. 

 XIY. Eruptive Rocks, 411-425. XY. Surface Geology; Glacial 

 Action, Ancient Lakes, Erosion by Running "Water and Atmospheric 

 Agencies, 426-477. XVI. Mineral Springs, with analyses, 478-487. 

 XYII. Structure and Age of the Rocky Mountain System, 488-501. 

 It is the result of 4 marked upheavals, at the close of the Carboniferous, 

 of the Trias, and of the Cretaceous, and during the Tertiary. W. W. 



Notes on the Geology of West Yirginia. No. II. Proc. Amer, 



Phil. Soc. Feb. 



. The Geological Relations of the Lignitic Groups. Proc. 



Amer. Phil. Soc. June. 

 Thinks these beds are Cretaceous. 



Strobel, P. Beitriige zur Kenntniss der geognostischen Beschaffen- 



heit der Anden, vom 33° bis 35° siidlicher Breite. [Geology of 



the Andes.] N. Jahrh. Heft i. pp. 56-62. 



Geological notes of a journey in parts of the Andes, supplementary 



to Prof. Stelzner's observations. Published in full in the author's 



*Yiaggi nell' Argentinia meridionale/ 1869, and abstracted in Peter- 



mann's * Mittheilungen,' 1870. F. W. R. 



Verril, Prof. A. E. Brief Contributions to Zoology from the Museum 

 of Yale College. No. XXXYI. On the Post-pliocene Fossils of 

 Sankoty Head, Nantucket Island ; with a note on the Geology, by 

 S. H. Scudder. Amer. Joum. ser. 3, vol. x. pp. 364-375. 

 ISIr. Scudder states that the fossiliferous beds of Sankoty, described 

 by Desor as lying unconformably upon Miocene clay, are really con- 

 formable, the clays belonging to the same series. Full lists of the 

 species found are given; those of the lower shell-bed are like those 

 now living in the protected bays of S. New England at from 3 to 

 5 fathoms ; whilst the upper shell-bed yielded an abundance of northern 

 forms, showing that it was deposited by the cold waters of the outer 

 coast, in shallow water, about 2 to 8 fathoma G. A. L. 



k2 



