460 J. LeConte— Formation of the 
wholl ellow, and closely approach in characters also the 
easy $ fad] American examples of var 
e American exe : 
the western form of this species has a longer tail than the east- 
ern one, and white, instead of dusky, eyelids, so also has that 
of G. Philadelphia (var. Macgillivray’). In the case of Myiar- 
chus Lawrencit, before alluded to, it is noticed that the yellow 
of the abdomen increases in richness, just at the same rate that 
the blackish of the pileum does in intensity, as it approaches its 
most southern extreme. ; 
{To be continued. } 
Meant 
Art. LVL—A Theory of the Formation of the great Features of 
the Earth's Surface; by Josepu LEContE, Prof. Geol. and 
Nat. Hist. University of California. 
[Concluded] 
As already stated, every other theory fails to account for the 
immense crushing together shown by plication and slaty cleav- 
age. Many theories take cognizance of this crushing, but in all 
it is a ec dinate accompaniment instead of the cause of the 
elevation. Let us examine very briefly some of the more recent 
theories, and show their inadequacy. ie 
__* For a discussion of this law see Baird, in this Journs 
vol. xli, March, 1866, 
/ 
