364 MESOZOIC FLORAS OF UNITED STATES. 



paper on the general subject, which he first read loefore the American 

 Philosophical Societ}^ in Philadelphia on January 6, 1888." In this 

 paper he not only proposed the name Albirupean for the upper beds, but 

 he also proposed the name Baltimorean for the lower ones, i. e., to quote 

 his words, "for the conspicuous clay formation which lies near the bottom 

 of the alluvial column on the Archean rocks of Maryland" (see pp. 47-48). 

 It must be remembered that all who had up to that date studied the 

 formation supposed that nearly or quite all the beds in Maryland were 

 higher than anj^ in Virginia, and the term "iron-ore clays," used by 

 Tyson, was used for the greater part of all this, although Professor Fon- 

 taine had observed that there were also gravels and coarse sands at 

 places in that State. Whether Professor Uhler intended his Baltimore 

 formation to extend into Virginia or not he does not say, and in this 

 paper he says that the Rappahannock freestone is lithologically different 

 from the white rocks of the Albirupean, which in fact is certainly the case. 

 He represents the iron ore as occurring in the Baltimorean across the 

 State in the form of pockets. His general description of the Baltimorean 

 may profitably be reproduced here: 



The formation is made up of numerous strata, constituting altogether a column of 

 alluvial matter more than five hundred feet deep. That part which we can examine 

 at or near the level of the lower streets in South Baltimore exhibits a dark lead- 

 colored compact clay, well stratified, and resting immediately upon a layer of dense 

 iron clay-stone only a few inches in thickness. Often the clay which comes in direct 

 contact with this stone is stained a bright red color, is of a very fine texture, and is 

 known as "pudding-claj-." On this the distinctly stratified layers of dark clay, 

 ranging usually from seven to nine feet in thickness, are built, and consist of strata 

 varying from three inches to fully two feet in thickness. Between the finely ground 

 layers, in contact with the smoothest surfaces, we meet with the remains of trees, 

 slu-ubs, vines, ferns, equisetas, and, perhaps, algte. These fossU remains occur in 

 the greatest profusion, accompanied by finely reduced lignite in the upper strata. 

 At least five such intervening plant-beds are present in the base of Federal Hill and 

 its extension eastwards, in each of which some peculiar form of fern, vine, or leaf 

 serves to distinguish it from the others. It has been my good fortune to discover 

 these beds in this region, and to secure ample collections of all the remains at present 

 found in them, and these are now being figured and described by Professor Fontaine, 

 of Virginia. 



» The Albirupean formation and its nearest relatives in Maryland, by P. R. Uhler: Proc. Am. Phil. Soc, 

 Vol, XXV, pp. 42-.53. 



