\ 



Zoology. 283 



evident that the present level of the lake has not varied materially dur- 

 ing the last six or seven hundred years. Such trees may be seen on 

 Portage Lake, Point Keeweenon, and also near the old trading post on 

 the north shore, north of Montreal River. Such a lapse of time or 

 even half its duration, would certainly enable present agencies to render 

 the above marks particularly conspicuous at the present water level. 

 But such does not appear to be the fact. 



I would here remark that the main body of the lake never freezes, 

 and that ice only forms along the shore and in the bays. Nor are 

 there any appreciable tides or currents in this lake except those pro- 

 duced by winds, and the unequal pressure of the atmosphere. There 

 are, however, a great many water worn and furrowed boulders with 

 longitudinal marks and scratches, at different heights all along from the 

 summits down to the level of the lake. Among them I have noticed 

 large blocks and boulders of conglomerate lodged on the summit of 

 greenstone ridges high above the conglomerate in situ, showing evi- 

 dently that the drifting current moved from the north to the south. 

 There are also vast beds of diluvium filled with such boulders, and par- 

 ticularly on the northern shore eastward of the Les Petits Ecrits, re- 

 peated terraced banks for miles in length, maintaining a horizontal 

 'jne with all the regularity of the present shore. These terraces ascend 

 •ike steps to the height of three or four hundred feet at least whilst re- 

 ceding about two or three miles. There can be no reasonable doubt 

 that the waters have at different successive periods prevailed at these 

 several different heights. The present level of the lake is reported to 

 J* six hundred and twenty seven feet above the tide of Hudson's Bay. 

 J- presume the drift furrows will be found on ail the prominent rocks 

 between these two bodies of water. So far as I had opportunity to ex- 

 amine, I invariably discovered them on the mountains intermediate. 



III. Zoology. 



1- Discovery of the Cranium of the Zevglodon; by M. Tuomey, 

 "tote Geologist of South Carolina, (Proc. Acad. Nat. Sen, iii, p. 152, 

 * e k, 1847.)— Early in January I was presented by F. S. Holmes, 

 ts q-> with a portion of the left upper maxilla, containing one tooth 

 J nd the alveola? of several others, which he discovered in the Eocene 

 oeds of Ashley river, about ten miles from Charleston. Soon •after, 

 , rof - Lewis R. Gibbes, of the College of Charleston, visited the same 

 locality, and had the good fortune to find the rest of the skull, much 

 factured, but so carefully were the fragments collected, that with a 

 ,ll V« patience we were enabled to restore them to their proper places. 

 [J. 1 * then altogether to these gentlemen that we owe the knowledge of 



^valuable fossil. . 



-° e -5crip^ on ._Occipital bone somewhat semicircular, transversely 

 flat or slightly concave, central portion thin ; a cresMfke ridge sur- 

 [ 0u nds the superior portion terminating in the suture with the temporal 

 ™ ne - Condyles two, articulating surfaces lunate, and almost enclosing 

 ine foramen magnum. Foramen magnum oval ; transverse diameter 

 }t inches, vertical diameter 1 inch ; transverse processes thick, spread- 

 ln 8i making the breadth of the base of the cranium equal to its diame- 



