754 THE JOURNAL OF GEOLOGY. 



are advanced for the extinction of these large reptiles. Professor Verril 

 regards lack of parental care as a cause ; Professor Marsh thinks the small 

 brain, highly specialized characters, and huge bulk, prevented them from 

 adapting themselves to changing conditions. Wood attempts an explanation 

 in the geographic changes. The flora, it is shown, changed almost as much 

 as the fauna. 



In attempting to extend his theories to periods of baseleveling antecedent 

 to the Mesozoic, the writer finds a check in the insufficiency of knowledge 

 concerning the early land forms. Comparison of meteoric baseleveling with 

 glaciation and submergence shows that only the first is conducive to land life, 

 that both glaciation and marine invasion are sterilizing in their effects. 



T. C. H. 



Tertiary and Early Quaternary Baseleveling in Minnesota, Manitoba, 

 and Northwestward. By W. Upham. (American Geologist, Vol. 

 XIV., No. 4, October, 1894.) 

 This paper forms an excellent supplement to the preceding one, taking up 

 the history where the other leaves off. The area, character, vertical extent, 

 etc., of the baseleveling of the northwestern plains during the Tertiary area 

 is followed by a discussion of the renewed elevation and partialbaseleveling at 

 the close of the Tertiary. Attempt is made to correlate this period of leveling 

 with one in Pennsylvania, New Jersey, the southern states, and in the West. 

 The origin of the Red River valley is found in this later erosion. Topo- 

 graphic features of Minnesota and Manitoba, due to the cycles of baseleveling, 

 are discussed, also the direction of the Tertiary and early Quaternary drain- 

 age. The last uplift, that at the beginning of Quaternary times, he says, raised 

 the area 3000 to 5000 feet higher than it is now, as shown by the fjords and 

 submarine valleys of the North Atlantic, Arctic, and North Pacific coasts. It 

 was the culmination of this uplift that brought the great snow accumulations 

 of the glacial period, under whose weight the land sunk below its present 

 level, causing the ice to melt. His approximate measures of the denudation, 

 along with some of his former estimales, give the duration for different periods 

 as follows : Tertiary, two to four million years ; the Lafayette, 60,000 to 

 1 20,000 years ; Glacial period, 20,000 to 30,000 years ; and the Recent period, 

 6,000 to 10,000 years. T. C. H. 



Proof of the Presence of Organisms in Pre- Cambrian Strata. Mr. L. 

 Cayeux. (Bull.de la Soc. Geol. de France, Ser y, torn 22<?, June, 

 1894, pp. 197-228.) 



Stratigraphy. — Radiolaria occur in beds of siliceous schists (phtanite of 

 Hauy) and quartzites of North Belgium, the position of which has been deter- 

 mined by Professor Charles Barrois. Their horizon is shown to be constant 



