24 J. W. Dawson—Footprints, etc., on Carboniferous Rocks. 
slicken-sided in this way, and which if wholly covered by this 
kind of marking could scarcely aa been recognized. I have 
red bodies of this kind in figs. 126 and 231 of my report on 
the Devonian and Upper Silurian plants, believing them, owing 
to their carbonaceous covering, to be probably slicken-sided 
fruits, though of uncertain nature. In every case I think these 
ies must have had a solid nucleus of some sort, as the severe 
pressure implied in slicken-siding is quite incompatible with a 
mere ‘“fluid-cavity,” even supposing this to have existe 
Prof. Marsh has well explained another phase of the influence 
of hard bodies in producing partial slicken-sides, in his paper 
on Stylolites, read before the American Association in 1867, and 
the application of the combined forces of concretionary action 
and slicken-siding to the production of the cone-in-cone concre- 
tions, which occur in the Coal-formation and as low as the Pri- 
mordial, was illustrated by the author in his Acadian Geology, 
676. 
“Of course, as I have not seen the specimens referred by Prof 
Geinitz to Gulielmites, but only the figures in his Memoir on 
the Permian plants of Saxony, I cann not offer any decided opin- 
ion as to their nature; but I have little doubt that the bodies 
mentioned by Mr. Ca rruthers are of the kind above referred to, 
and would be found to have had a solid nucleus either organic 
or of some other kind. 
I may remark in conclusion that it would be well if collectors 
would give some attention to imitative markings an 
footprints of the kinds above referred to, as well as to their 
mode of occurrence with reference to the surfaces and material 
of the beds on which they are found. The labors of Hitchcock 
and others show how much interesting information may thus 
be obtained, and many mischievous errors might also be avoided. 
nmy own studies in fossil bota tany, [ have made it a point to 
collect and study all markings resembling plants, as well as the 
effects of crumpling, pressure, concretionary action, crystaliza- 
tion, shrinkage and slicken- siding upon actual vegetable re- 
mains; and by so doing I have avoided the trouble and expense 
of describing and figuring some dozens of imaginary species; 
while it would be easy to point out in works of some pretension 
costly figures and elaborate descriptions based on imitative 
forms or distorted and otherwise altered fossils. 
