270 ‘The American Naturalist. [March, 
drift is traceable to the mountainous region of Trans-Pecos Texas, 
where nearly every variety of pebble can be found in its original loca- 
tion. Second, the country between the Nueces and the Brazos. This 
region is covered with pebbles, gravel and sand derived from the rocks 
found in the Central mineral region. Third, from the Brazos to the 
Sabine, where the gravel is largely made up of ferruginous material 
which had its origin in the iron-capped hills which cover so large a 
portion of Eastern Texas. Fourth, the area known as Northwest 
‘Texas according to the survey division. The drift of this region came 
from the hills enclosing the waters under which they were deposited, 
viz., Wichita Mountains and the mountains of New Mexico.—Trans. 
‘Texas Acad. Sci., Vol. i, 1892. 
Archean.—According to Mr. H. V. Winchell, Minnesota possesses 
the greatest iron district known in the world to-day. It lies in the 
Mesabi range and extends from the Canadian boundary line in a direc- 
tion a little south of west, beyond the Mississippi River, a distance of 
140 miles. The ore on the eastern end is hard, black and magnetite, 
owing to the heat of the gabbro overflow. In the central and western 
portions of the range the ore is soft hematite, limonite and geothite. 
As to the source of the iron, it is believed by Mr. Winchell to be 
largely the result of oceanic deposition, both chemical and mechan- 
ical, and to have been concentrated in its present situations. (Twentieth 
Ann. Rept. Minn. Geol. Surv., 1892).—Mr. T. R. Struthers advances 
the theory that the primitive rocks, i. e., granite, were formed by the 
cooling of the exterior of the globe under the primeval deep. The 
pressure of the sea at the depth of two miles would be sufficient to 
account for the structure of granite. This theory explains the fea- 
tures presented by the bedded or stratified granite of the British 
islands and many other parts of the world. (Geol. Mag., Dec., 1892.) 
Paleozoic.—A skull of Dinichthys intermedius recently examined 
by Professor E. W. Claypole supplies details previously unknown 
regarding the plates of which it is composed. The especial points of 
interest are the forms of some of the plates and the over and underlap 
- which has not been represented, and sore additions to the structure of 
the upper jaw. (Am. Geol., Oct., 1892.)—Mr. Herbert Bolton reports 
a triolobite from the Skiddaw slates of the Isle of Man. The specimen 
belongs to one of two genera, Asaphus or Æyglina, both of which are 
Ordovician forms. This in connection with the occurrence of two 
specimens of Palzeochorda (an Arenig form) is strong evidence that 
