CLINTON GROUP. 
69 
14. 
Fucoides Gracilis. 
This species is one of the most delicate of the marine plants preserved in our rocks, and 
the specific name of gracilis is proposed. The branches sometimes appear as if nodulose or 
vesicular. The specimen figured is probably only a branch from a larger individual. It will 
be observed that the stem and lateral branches are of equal size ; it was therefore a floating 
and probably a flexible plant, as the stem could not have supported branches of its own di¬ 
mensions. This species beautifully contrasts with the strong and rigid forms from the same 
group farther east. 
In the Fourth District, the lower limestone, as its name implies, is eminently characterized 
by the presence of the Pentamerus oblongus of Murchison. This fossil exhibits a great variety 
of form as well as of size. The shells are nearly all broken, and so packed together as to 
indicate that they have been drifted by a current or washed by the waves, while the mass 
formed the margin of the oeean or an elevated portion of its bed. At Rochester they become 
an entire layer of about one foot in thickness, but farther east they are distributed throughout 
the whole rock, and bear evidence of much wearing before being imbedded; they are also 
frequently much intermixed with green shaly matter. 
The following woodcut gives illustrations of some of the common forms. 
