+ 
warp.] JURASSIC CYCADS FROM WYOMING. 391 
The peculiar outer coating or second armor of the Jurassic cycads of 
Wyoming obviously constitutes a good generic character. At the same 
time, as is seen by the above descriptions, it is wholly different from 
that of any other genus of cycadean trunks, and it is therefore neces- 
sary to regard it as a new genus, altogether different in its most essen- 
tial generic characters from any other. From the generally small size 
of these trunks, especially when compared with the giant forms of the 
Black Hills, I have concluded to call this new genus Oycadella. 
Although a macroscopic examination is sufficient to show this generic 
distinction, still it does not immediately indicate the true nature of this 
supplementary envelop. I was at first disposed to think that it con- 
sisted of matted leaves. I observed that the leaf bases were always 
present, filling the scars, and. sometimes projecting somewhat above 
the general surface, and I did not know but that expanded portions of 
them might have also persisted and been rolled and packed against 
the trunks in the process of entombment in a manner to produce the 
observed effect. Buta strong glass failed to bring out the difference 
on the surface that would be expected if such had been the case: stri- 
ations, folds, leaf margins, etc. Moreover, the fractured margins often 
showed the darker leaf bases coming out to the surface of the true 
armor but never continuing across the line of separation and mingling 
with the tissue of the outer layer, which is sometimes more than a 
centimeter in thickness. 
Since, aside from the reproductive organs, less abundant than in the 
Cretaceous cycads, the armor consists of nothing else than the leaf 
bases and the ramentum that is attached to them and constitutes the 
walls, this last must have furnished the covering which forms the 
outer coat. It has been observed that these fine scales or hairs are 
always the most certain to be preserved, and whatever the degree of 
imperfection in the state of preservation in other respects, the walls 
are usually intact. This accounts for the large number of trunks that 
consist of these walls penetrated to a great depth by the rhombic or 
triangular cavities, looking like petrified honeycomb or sponges. 
This is a most fortunate circumstance, since otherwise we should in 
such cases have nothing but the woody cylinder of the trunk, and 
would be entirely incapable of determining the true nature of the 
objects. 
This special susceptibility to petrification on the part of the ramen- 
tum explains the presence of the external covering of the Wyoming 
Jurassic cycads, since it seems actually to consist of a matted mass of 
these ramentaceous hairs, which in some way developed so luxuriantly 
upon the sides of the petioles as to push out beyond the surface and 
roll over the spaces formerly occupied by the leaves and fruits. It 
seems necessary to assume that this occurred long after the fall of the 
