MESozoic. 259 
Eastern Trias, but the systems have been most studied in their 
paleontological relations, which are given in the statement by 
Prof. Cope. 
2. The Cretacic. This system is well represented in the 
United States. It is well developed in New Jersey, where its study 
by naturalists from Philadelphia and New York was first begun. 
It is there represented by the series of Raritan Clays and 
their included beds of sand below, which are of estuary origin, 
and the series of greeusands and limestones above. It is also 
well represented in the Atlantic States farther south, and in the 
Gulf States by series closely resembling these. In the States 
west of the Mississippi it has enormous development, and though 
the material representing the stages varies much from that of the 
eastern ones, the abundance of fossils, both animal and vegetable, 
is such that their correlation with those of the East is well shown. 
The tabular statement below shows the position of the series in 
this System as fully and closely as yet determined, and the 
Rocky Mountain section shows the development of the Cretacic 
near the northern boundary. 
In this tabular form of showing the members of the Cretacic 
Series, it will be understood that their correlation is not abso- 
lutely assured. Dr. Newberry's studies lead him to the eouclu- 
sion that the Raritan clays are as recent as the Upper Green-sand 
of Europe and perhaps nearer the Lower Chalk. Prof. Whit- 
field's work in the Paleontology of the Cretacic leads him to 
think the Lower Green-sand marl bed of New Jersey is of the 
same age with the Ripley group of the southwest States, — some 
others place the Ripley group very high in the Upper Cretacic ; 
and the correlation of some of the lower members of the series 
is very far from being settled. The Alabama-Mississippi state- 
ment is from the surveys of Smith and Johnson, as given in Bul- 
letin 43 of the U. S. Geol. Survey ; that of Texas, from R. T. 
Hill's paper in the Am. Jour, of Science, vol. xxxiv. (3d ser.), p. 
287. The Potomac is inserted from the paper of W. J. McGee, 
in Am. Jour. Sci., vol. xxxv. (3d ser.), p. 120. The North 
American is from the Reports of Meek, Hayden, King, Cope, 
White, and others. 
That of the Rocky Mountains is from the Report of G. M. 
Dawson, in the Geol. Report of Canada for 1885, B, page 166. 
