Lesquereux. | 170 (Oct. 19, 
of the vegetable fragments embedded into the clay. Another specimen not 
figured is larger, seven centimeters in diameter, nine centimeters long, 
nearly exactly cylindrical, with irregular more or Jess distinct ribs, marked 
crosswise by large wrinkles or irregular protuberances, which do not 
show any distinct relation of form and position between them. Therefore, 
both these fragments are identified merely by their cylindrical shape, rep- 
resenting stems or branches, and by their common habitat. The compound 
of both is exaetly of the same matter, a hard bluish clay or marl mixed 
with grains of coarse sand. This compound has taken the place of the 
woody matter destroyed by maceration, and therefore nothing is left of 
the original vegetable fragment but the outline of the stems and the im- 
pression of the scars of the bark. 
The fact of the total disappearance of woody fibres in fossil specimens 
cannot afford an argument against their reference to land plants ; for even 
in the coal measures, trunks of Sigillaria, Lepidodendron, etc., are very 
often recognized in sandstone merely by cylindrical outlines of the 
trunks, and impressions of the scars of the surface of the bark. This mode 
of petrification is general for isolated fragments of wood. 
As related to the same kind of vegetable we have a fragment, fig. 8, 
found near Cincinnati, in strata of the Cincinnati group, and which con- 
firms the reference of the specimens discovered by Dr. Scoville both to 
the locality named, Longstreet Creek, and also to the formation of the 
Cincinnati group. This specimen at the same time represents more evi- 
dently the Sigillarioid character by its rhnomboidal form, the cicatrices and 
their position in spiral being still more distinctly seen than in fig. 7, 
though the piece of bark whose impression is so well preserved has been 
apparently flattened by compression. No trace of vascular scars is re- 
marked however. These scars are generally erased in specimens whose 
surface bark has been decomposed and destroyed. 
As remarked above, cicatrices of the same character, often without cen- 
tral points, are seen on the surface of the bark of Artisia, Leptophleum 
rhombicum, Sigillaria Brardii, S. Defrancti, and other species of the coal. 
I have a remarkably fine branch of an Ulodendron from the Cannel coal 
of Pennsylvania, which bears outside cicatrices exactly like those of fig. 7, 
with oval central vascular scars. The size of this branch is about the 
same, for it measures twenty centimeters in length, and is only twenty 
two millimeters broad, though slightly flattened. Its impression into 
cannel coal is perfectly distinct. Hence the objection against the reference 
of the specimens of the Silurian to land plant on account of their small 
size is groundless. 
On the reign of organized beings to which these fragments are referable 
there can be therefore no doubt, for considering merely the size of the 
stems and their cylindrical form they evidently represent plants. 
The question is therefore on the relation of the stems to land or marine 
plants. Besides the authorities which have been quoted as regarding as 
evident the relation of these fossil remains to land plants, the analogy of 
