92 abstracts: geology 



presence of either lead sulphate or barium sulphate, the two sulphates 

 most commonly used in rubber goods. The accuracy of the determina- 

 tion is satisfactory for all practical purposes. J. B. T. 



GEOLOGY. — The stratigraphy of the Montana group. C. F. Bowen. 

 U. S. Geological Survey Professional Paper No. 90, pp. 95-153. 

 1915. 



Because of differences of opinion which have arisen regarding the 

 age and stratigraphic position of the Judith River formation, a study 

 of the stratigraphy of the Montana group was undertaken. 



It is shown that the Judith River formation has been traced continu- 

 ously from areas wher^ its position beneath the Bearpaw shale is un- 

 disputed into the western part of the type area (namely, at the mouth 

 of Judith River) and has been found to be identical with the Judith 

 River at that locality. 



The paleontologic evidence shows: (1) that the argument that the 

 Judith River formation overlies the Fox Hills is unfounded; (2) that the 

 flora of the Judith River formation is of Montana age; (3) that the 

 invertebrates of the Judith River formation are more closely allied 

 to the Belly River than to the Lance; (4) that if the Judith River is 

 to be made the equivalent of the Lance on the basis of the similarity 

 of the vertebrate fauna, the Belly River must on the same evidence 

 also be made the equivalent of the Lance formation; (5) that the Cera- 

 topsidae, which form so important an element of the Lance fauna, 

 are generically and specifically unlike the representatives of that family 

 in the Belly River and Judith River faunas. The palaeontologic evi- 

 dences therefore indicating a closer relationship between the Belly 

 River and Judith River than between either of these formations and 

 the Lance are in accord with the stratigraphic evidence, which shows 

 conclusively that both the Judith River and Belly River formations 

 are separated from the Lance by a marine formation which is of un- 

 doubted Cretaceous age. R. W. S. 



GEOLOGY. — Erosion intervals in the Eocene of the Mississippi embay- 

 ment. E. W. Berry. U. S. Geological Survey Professional Paper 

 No. 95, pp. 73-82. 1915. 

 The older Tertiary deposits of the Gulf Coastal Plain, comprising 

 several thousand feet of sands, clays, marls, lignites, and impure lime- 

 stones, have always been considered as forming an uninterrupted and 

 conformable series, extending from the lower Eocene to the top of the 



