996 The American Naturalist. : [November, 
General Notes. 
GEOLOGY AND PALEONTOLOGY. 
The Laurentian of the Ottawa District.—In a paper recently 
published by Mr. R. W. Ells, the author shows that certain modifica- 
tions of the arrangement of the Laurentian strata as laid down in the 
geological map of Canada, 1866, must be made. While it is as yet 
hardly possible to estimate correctly the thickness of the strata, there 
is no doubt that it has been overstated. The Anorthosite masses north 
of St. Jerome which had been placed in the upper Laurentian have 
been shown by Dr. F. D. Adams to be of intrusive origin. The lime- 
stones in both the Trembling Mountain section and the region between 
the Anorthosite area and Gatineau River in nearly every case occupy 
well defined synclinals. 
The succession of strata in ascending order as revised by Mr. Ells is 
as follows: 
1. Reddish-gray gneiss without distinct signs of bedding. 
2. Reddish orthoclase gneiss showing a well stratified arrangement 
of beds. 
3. Grayish and rusty gneiss passing into a regular crystalline line 
stone. 
4. A series of schistose oti _highly metamorphic, described in 
earlier reports as the Hastings se 
In conclusion the author calls get to the fact that under the 
present arrangement of the Laurentian of Quebec the parallelism with 
the rocks of the system as displayed in southern New Brunswick is very 
close. (Bull. Geol. Soc. Am., 1893.) 
Relations of the Laurentian and Huronian Rocks North 
of Lake Huron.— This paper is an extension of one published by the 
author, Mr. A. E. Barlow, in 1890, and contains some further observa- 
tions on the nature of the contact between the Huronian rocks of Lake 
Huron, described by Logan and Murray, and the Laurentian gneisses. 
As a result of his investigations, Mr. Barlow is convinced of the irrup- 
tive nature of this Laurentian gneiss and of its magmatic condition at 
a time subsequent to the petrification of the Huronian sediments. The 
following facts have led to this conclusion:— (1) The diverse strat 
