MEDINA SANDSTONE. 
7 
The whole substance and 1 arrangement is angular, and there is some reason to hesitate in 
assenting to its organic character. It covers large surfaces of the stone ; and there is no evi¬ 
dence, on the largest slabs obtained, of any thing like a commencement or termination of the 
structure. Every branch or reticulation is connected with the stone by the small rootlike fibres, 
as in the figure ; and surfaces several feet in extent present no deviation from the general 
character given in this figure. The surfaces thus covered present a most singular and beautiful 
appearance ; and when in some cases covered by ripplemarks, the interesting character is 
greatly enhanced. 
Position and locality. This peculiar form is known only in the terminal gray portion of the 
rock (gray band) at Medina in Orleans county. {State Collection.) 
Fucoifjles. auriformis, and F. heterophyllus. Report of the Fourth Geological District of New- 
' York, 1843, p. 47. 
Fig. 4. Surface covered with irregular auriform elevations, single or overlapping each other. 
These appear like casts of soft material, made in cavities in the rock below. 
Fig. 3 has a still more artificial character, presenting irregularly rugose or striated elevations 
which have no prevailing or definite shape. 
These forms, were described in the Report of the Fourth District as different species of 
Fucoides ; but I have not, up to this time, been able to satisfy myself that they are organic. 
They appear among the many curious and remarkable markings which cover large surfaces in 
the Medina sandstone and Clinton group, but which can scarcely be referred to organic remains. 
A shallow sea,, with the proximity of beaches and sudden transitions in the nature of the de¬ 
posits, have produced many appearances upon the surface that at first view might be attributed 
to organic influences, but which are doubtless due to the influence of waves, currents, and 
perhaps to other dynamical causes. 
The kind of markings in question are found abundantly at Rochester, and also at Medina 
and other places in Western New-York. (state Collection.) 
387. CHiETETES - \ 
Pl. IV. Fig. 1. 
This species is undistinguishable from the branching forms in. the Trenton limestone, and is 
represented here from the interesting circumstance of occurring in the Medina sandstone at 
