WARD.] JURASSIC CYCADS FROM WYOMING. 389 
in photographing the specimens it is observed that the dark surfaces 
come out almost as clearly as the light or variegated ones. 
Besides the lime incrustations on the under surface, there was 
usually a coating of lichens on the surface'which lay uppermost, and 
this, where it existed, was quite as fatal to an examination of the parts 
thus concealed as the coating of lime. This, though somewhat more 
difficult to remove, yields to a strong alkali, which has no effect upon 
the underlying structures. 
The cleaning of the specimens by both the processes employed was 
undertaken as soon as possible after the collection had been unpacked, 
and I commenced the systematic study of the trunks almost at once, 
thoroughly noting and recording the characters and peculiarities of 
‘every specimen and of all parts of each, and by the end of May, 1899, 
I had completed this part of the work. I have compiled tables of the 
characters, and the subdivision into specific groups has been based 
mainly upon such characters. Notwithstanding considerable sameness 
among these characters, it is possible to classify them, and there seems 
no doubt that, could their foliage and reproductive organs be known, 
the cycadean flora of the Jurassic of Wyoming would be represented 
by a considerable number of species if not of genera, although it 
would be rash to assert that the lines would be drawn in all cases where 
we must draw them here. 
The most marked feature that struck me on first casual inspection 
of these trunks, aside from their relatively small size, light color, and 
soft calcareous structure, was the frequency of a sort of smooth, to the 
naked eye structureless, dull, uniform covering that invests their outer 
surfaces and cuts off the view of the normal organs of the armor. A 
closer examination revealed the fact that this was not an occasional con- 
dition, but the normal state of these cycads, and that the cases in which 
this outer coating is wanting represent the abnormal state. It further 
became clear that there really are no cases in which it is naturally 
absent, and that its absence is always due to some external influence 
acting upon the surface which has removed it. There isan abundance 
of proof of this, and most of the specimens show parts over wuich the 
external coating still adheres and other parts where it is absent. The 
latter usually reveal the nature of the agency that has removed the 
coating—whether a sudden and violent concussion, gradual erosion, or 
a process of weathering. The contact of the outer layer with the sur- 
face of the armor proper is always marked by a clear plane of separa- 
tion, and usually by an open structure or even a partially void space. 
This becomes a natural plane of cleavage, and almost any influence will 
cause the outer coating to scale off like the outer bark of a tree. 
In the specimens of the Yale Museum this outer coating had almost 
entirely disappeared, though not absolutely, so that the phenomenon 
