318 GEOLOGY AND MINERALOGY. 



of the boulder clay or partly imbedded iu it, were covered with the remains of 

 marine creatures, especially Bnlanus orenatua, Spirorbis sinistrorsa, Spirorbis 

 spirillum, Lepralia and Hippothoa. This layer, in short, evidently represented a 

 time when the surface of the boulder clay, covered only by a thin layer of sand 

 and stones, constituted the bottom of clear and deep water, before it became 

 covered by the Saxicava sand. Tliis bottom, although no clay has been deposited 

 on it, represents the Leda clay at Montreal, and is exceedingly rich in the fossils 

 usually found at the surface of that bed, Foraminifera occur in it, but they are 

 comparatively rare, and so far as I could find, only of species common at Montreal." 

 These facts, with others detailed in the paper, appear to confirm fully the three- 

 fold subdivision of our Post-Tertiary deposits, as established by the author from 

 his previous researches, viz. : an underlying non-fossiliferous boulder clay ; a deep- 

 water bed of clay or sand, the '' Leda clay" of Montreal, and the overlying shal- 

 low-water sands and gravels, the " Saxicava Sand" of Professor Dawson's original 

 classification. Exclusive of doubtful forms, no less than sixty-three species of 

 marine invertebrata have been obtained, chiefly by the author's explorations from 

 these Post-Tertiary bads of the St. Lawrence Valley. 



GEOLOGY OF CAKfADA, <fcC. 



The May number of the Journal of the Geological Society of London contains aa 

 (interesting sketch from the pen of Professor Ramsay, of our Surface Geology and 

 Drift formation generally. Although containing nothing absolutely new, this paper 

 may be consulted with much profit, as an able resume of the known facts of the 

 subject, classified and discussed with great perspicuity. To European Geologists 

 it will be especially acceptable. The following is Professor Ramsay's summaiy 

 of its contents : Glacialized condition of the Laurentine Mountains, and the drift- 

 deposits of Montreal. Glacial drift of the plains ; striae ; and roches moutonnees. 

 Drift and strise in the Valley of the Hudson, including the Canaan Hills and (he 

 Catskill Mountains. Probable equivalency of the upper clay drift of the Hudson 

 Valley with that of Lake Champlain and of Montreal. Probable date of the 

 Niagara Falls. Drift and other late Tertiary deposits at Niagara. 



GNATHODON DEPOSITS OP MOBIILE BAY. 



Jn a brief notice, in the May number of Silliman's Journal, of the "Second 

 Biennial Report on the Geology of Alabama " by the late Professor Tuomey, it is 

 stated that the celebrated " gnathodon beds " of Mobile Bay, regarded as fossil 

 deposits by Sir Charles Lyell and other geologists, " are, beyond doubt, accumu- 

 lations made by the aborigines of the country. They are often in heaps, and 

 contain ashes, burnt shells and charcoal, and bear no evidence of accumulation by- 

 wave action." The Report is edited by Professor Mallet, Chemist of the Alabama 

 Survey. 



CRETACEOUS FORMATION OF KANSAS AND NEBRASKA. 



Most of our readers are probably acquainted with the fact that certain strata 

 cantaining dicotyledonous leaves in great profusion and variety, have been recog- 

 nized in different parts of Kansas and Nebraska. The true age of these fossil 

 leaves, and their associated beds, is a question of so much geological importance, 



