Section IV, 1891. [ 29 ] Trans. Roy. Soc. Canada. 



IV. — Two Species of Trees from the Post-Glacial of Illinois. 

 By D. P. Penhallow, B.Sc. 



(Read May 27,1891.) 



Last year Prof. 0. Marcy, of Evanston, Illinois, transmitted to me two specimens of 

 fossil wood for determination. One was obviously an oak and the other a coniferous 

 wood of some kind, which Prof. Marcy thought possibly might be a Thvya. Both were 

 in such a state of preservation as to admit of treatment with caustic potash, and the sub- 

 sequent preparation of sections with an ordinary microtome. The sections showed the 

 structure to be on the whole well preserved, though in the oak, somewhat modified by 

 decay and pressure. 



G-EOLOGiCAL Position. 



From the data furnished by Prof. Marcy, I am able to make the following statement 

 respecting the geological position of these plants : — 



As appears from the accompanying map,' three lake ridges are prominently develop- 

 ed in the immediate neighborhood of Chicago. Two of these, the middle and lower 



a-- 2S) 



7 2. 



i ,. 1- ^, ,1 50 



Fio. 1. 

 beaches, have their western terminations on the shores of the present lake at Evanston, 

 where the water has so encroached upon them as to make a cutting, exposing the ridges 

 in section. The relations of the various deposits thus brought to view are exhibited in 

 the sectional figure (fig. 1). 



' Plate III. 



