92 THE CANADIAN NATURALIST. [April 



ciliae, the cells of the ciliae irregularly cylindrical. W. Mexicana 

 Fee, as figured, has an involucre somewhat resembling this one, and 

 I suppose it may belong to the same group. 



5. Woodsia obtusa. Torrey, Cat. PL in Geol. Report of New 

 York, 1840. Hooker, Species Filicum, i, p. 62. Polypodium 

 obtusum, Swartz, Syn. FiL, p. 39. 



Hab. — New England to North Carolina, and westward to Wis- 

 consin and Missouri. (On the Columbia River, Hook. Fl. Bor. Am., 

 but the specimens are more likely to be W. scopnlina.') Specimens 

 from Texas, Ch. Wright, Nos. 830 and 2120, I refer to this species 

 somewhat doubtfully, as the involucres are cleft into very narrow 

 laciniately fringed lobes. Better specimens are needed to show 

 what the plant really is. 



New Haven, Connecticut, U. S. A., March 15, 1865. 



ON THE OCCURRENCE OF ORGANIC REMAINS IN 



THE LAURENTIAN ROCKS OF CANADA .* 



By Sir W. E. Logan, L.L.D., F.R.S., F.G.S. ; Director of the Geological 

 Survey of Canada. 



The oldest known rocks of North America are those which com- 

 pose the Laurentide Mountains in Canada and the Adirondacks 

 in the State of New York. By the investigations of the Geological 

 Survey of Canada, they have been shown to be a great series of 

 strata, which, though profoundly altered, consist chiefly of quart- 

 zose, aluminous, and calcareous rocks, like the sedimentary de- 

 posits of less ancient times. This great mass of crystalline rocks 

 is divided into two groups, and it appears that the Upper rests 

 unconformably upon the Lower Laurentian series. 



* This, and the three following papers, by Messrs. Dawson, Carpenter 

 and Sterry Hunt are reprinted from the Quarterly Journal of the Geo- 

 logical Society of London, for February, 1865. Some additional notes 

 by the authors and editors are distinguished by being included in brack- 

 ets. See also a supplementary note by Dr. Dawson, on the discovery 

 of Eozoon in Ireland on page 126. 



In place of the lithographed plates published in the Quarterly Journal 

 to illustrate the papers of Messrs. Dawson and Carpenter, selections from 

 those, filling a single plate, are here given; besides which three wood- 

 cuts are added. — Eds. 



