WARD] JURASSIC CYCADS. 377 
not overflowed in the dry season. Here was a fine opportunity to 
examine them, and although it is usually difficult to obtain large slabs 
lying in such a position, yet, from the easy cleavage and generally 
workable character of these slates, we were able to work out fine 
pieces and secure good specimens. The slates here are nearly ver- 
tical; in fact, there seems to be an easterly dip, as if they were 
tilted more than 90°. They have a thickness of about 200 feet, with 
no conglomerate bands. They are full of plants of typical Jurassic 
types. Most of the Olalla Creek forms occur, including the Ginkgo 
and the leading cycadaceous genera, Ctenis, Ctenophyllum, Pteroza- 
mites, Pterophyllum, etc. Some of the same ferns, notably a narrow 
Angiopteridium, were found present at nearly all the Buck Mountain 
localities. Besides these, a number of forms not seen farther north 
were collected, including many long, narrow coniferous leaves resem- 
bling those of Cephalotaxus or Taxodium, but showing fine transverse 
striee on both sides of the midrib. A large collection was made. 
Professor Diller and Mr. Brown worked out the stratigraphy in the 
same manner as in the Buck Mountain district. It is more compli- 
cated, and the Knoxville beds occur on Iron Mountain Creek not more 
than a mile east of the Jurassic outcrop. Eocene plant-bearing beds 
lie on the hills on both sides of Cow Creek, and it is evident that much 
still remains to be done before all will be made clear, but the general 
fact seems established that a Jurassic deposit of unknown extent and 
of considerable thickness trends through these mountains from north 
to south, which can no longer be overlooked in treating the geology 
of Oregon. 
CYCADEAN TRUNKS FROM THE JURASSIC. 
A considerable number of cycadean trunks have been found in beds 
that are referred with more or less certainty to the Jurassic. There 
are as yet, however, only two sources of such material, and one of 
these is of doubtful age and is only represented by a single specimen. 
This locality is in Colorado. The other locality is in Wyoming, and 
there is no doubt as to its Jurassic age. I will treat the Colorado 
trunk first. 
THE BOULDER CYCAD. 
Early in the summer of 1896 Dr. F. H. Knowlton and Dr. T. W. 
Stanton, in passing through the museum of the State School of Mines 
at Golden, Colorado, observed a cyeadean trunk on exhibition there, 
and made inquiries relative to its source. In a letter which I received 
from Dr. Knowlton soon after this, dated June 18, 1896, he says: 
Dr. Stanton and I visited Golden yesterday, and as a preliminary went through 
the collections belonging to the State Mining School. One of the first things that 
I saw was a beautiful silicified cycad trunk. It was about 2 feet in height, regularly 
