259 



phanus Loganianus, Pleuromya subcompressa, Astarte Packardi, Trigonia 

 JDawsoni, Grammatodon inornatus, Camptonectes extenuatus and Gryphcea 

 Nebrascensls) hold also Modiola (or Volsella) formosa of Meek and 

 Hayden, and Gervillia Montanaensis of Meek. 



The discoveiy in the Black Hills of Dakota of deposits which were 

 supposed to be of Jurassic age, principally upon palseontological grounds, 

 was first announced by Mr. F. B. Meek in 1858, and since that time 

 numerous species of fossils from rocks of a similar geological horizon 

 in Utah, Montana and other Western States and Territories, as well as 

 in California, have been described by Mr. Meek, Professor E. P. Whit- 

 field and Dr. C. A. White. 



The reasons which induced Mr. Meek to regard certain strata in Utah 

 and Dakota as Jurassic are clearly stated on pages 110 and 111 of 

 Dr. Hayden's " Geological Eeport of the Exploration of the Yellow- 

 stone and Missouri Eivers" and elsewhere, but the conclusions at 

 which Mr. Meek arrived, with the somewhat meagre material at 

 his disposal, although such as any paleontologist would probably have 

 come to under the circumstances, appears to the writer to be outweighed 

 by the additional evidence afforded by the large collection of fossils 

 since made by Mr. Eichardson and Dr. Dawson at the Queen Charlotte 

 Islands and on the mainland of British Columbia, which throw an 

 entirely new light on the subject. 



Throughout the Western States these supposed Jurassic rocks are 

 everywhere stated to occupy a position immediately below the sand- 

 stones and conglomerates of the " Dakota Group " (which Meek main- 

 tains is the equivalent of the English Upper Green Sand) and as 

 immediately above certain red beds which are generally believed to be 

 Triassic. Wherever these ostensibly Jurassic rocks occur, therefore, 

 it follows that part of the Mesozoic series is wanting, and it is difficult 

 to understand why the Lower Cretaceous and earlier half of the Middle 

 Cretaceous should always be missing and not the Jurassic. 



As will be seen a little farther on, there are good reasons for 

 supposing that the Agglomerates and Lower Sandstones of the Queen 

 Charlotte Islands form part of the same formation as the Lower 

 Shales, but, whether this be the case or not, the three together occupy 

 almost exactly the same stratigraphical position as the supposed 

 Jurassic rocks of the Western States. At Cumsbewa and Skidegate 

 Inlets the Lower Shales immediately underlie conglomerates which 

 are probably synchronous, or nearly so, with those which almost 

 invariably occur at the base of the " Dakota Group," and the Lower 

 Sandstones are succeeded by Upper Triassic rocks, although the two 

 latter are unconformable. 



Turning next to the palseontological aspect of the question, Mr. 



