204 



REVIEWS 



marl the phosphate was in the form of pebbles and more finely divided 

 material. As the result of a long period of erosion covering most of the 

 Miocene, the phosphatic materials accumulated at the surface and were 

 reworked by the Bone Valley sea. The river-pebble deposits have 

 been formed in the beds of streams that have lowered their channels 

 into either the Alum Bluff or the Bone Valley phosphate horizons. 



W. B. W. 



Lewis and Gilmer Counties. By David B. Reger. West Virginia 

 Geol. Survey, 1916. Pp. 660, figs. 12, pis. 30, maps 2. 



Several volumes each year are added to the excellent county reports 

 already published by this state. Lewis and Gilmer counties, located 

 near the center of the state, have large coal deposits and are rich in oil 

 and gas. Some of the largest gas wells of the Appalachian field were 

 drilled in Lewis County. 



The Pennsylvanian formations do not reach the development in 



these counties that is reported from areas to the south and west. The 



Pittsburgh seam of the Monongahela series carries the principal coal 



reserve, and the oil and gas sands range in age all the way from the 



Chemung to the Dunkard series. 



W. B. W. 



The Montana Group of Northwestern Montana. By E. Stebinger. 

 Professional Paper, U.S. Geol. Survey, No. 90-G, 1914- 

 "Shorter Contributions to General Geology, 1914-" Pp- 

 61-66, fig. 1. 

 The Montana group of northwestern Montana is composed of four 

 conformable formations which are, in ascending order: the Virgelle 

 sandstone (220 feet thick) which is chiefly marine, the Two Medicine 

 formation (1,950 feet thick) which is mainly a fresh-water deposit, the 

 marine Bearpaw shale (490 feet thick), and the brackish and marine 

 Horsethief sandstone (360 feet thick). These formations are similar 

 to those of the Montana group described in southern Alberta by Dawson, 

 but differ decidedly from those in the central part of Montana. The 

 Belly River series of southern Alberta is equivalent to the Virgelle sand- 

 stone plus the Two Medicine formation, and these in turn are equiva- 

 lent to the Eagle, Claggett, and Judith River formations (of central 



Montana) combined. 



V. O. T. 



