MEDINA SANDSTONE. 
49 
vegetable forms generally. The spaces produced in this manner are various in form and 
unequal in size, as will be seen in the figure, which is a faithful representation of a specimen 
from Medina, now in the State Collection. The surfaces of the stratum where this fossil 
occurs often present beautifully defined ripple marks. Mr. Conrad thus describes these ap¬ 
pearances : “ Upon this surface there is a beautiful fossil, which consists of stems or branches 
joined in a reticulated manner, and having undulated lateral root-like fibres. This fossil is 
spread over a considerable space, and I noticed that in some instances it followed the undula¬ 
tions of the ripple marks: it was therefore pliable, and moored by its root-like fibres to a 
sandy bed, over which a current of water ran, producing such impressions as we see caused 
by tidal currents on a sandbar.”* 
Ripple Marks. 
These evidences of shallow water do not appear in the lower division of this rock, at any 
locality which I have visited ; and their absence fully accords with the other facts implying 
a rapid deposition in comparatively deep water. Only when we come into the Second divi¬ 
sion of the mass, do we find some imperfect markings of this kind, nor do they occur in any 
degree of perfection except in the higher strata, and in few localities. At about the termina¬ 
tion of the quartzose deposit, and in all the higher portions of the rock, they are of frequent 
occurrence, and often in great perfection. The specimen from which the accompanying il- 
7. 
Geol. 4tii Dist. 
Geological Report for 1837. 
7 
