46 
GEOLOGY OF THE THIRD DISTRICT. 
change in the mineral character, but they are accompanied by other fossils which had no 
existence in the Trenton rock. Fossil-like minerals have also a two-fold character; one 
which depends upon themselves as individuals, the other from association. 
As a point or term of comparison for distant localities, the Trenton limestone, from the 
number of its fossils, as to class, genera, species and individuals, is one of the most important 
rocks of the lower part of the New-York system. In parts, it is loaded with, the remains of 
animal life. In the preceding rocks there was but the dawn; in this, a full existence as to 
different kinds, and numbers especially of different kinds. 
4 . 
The fossil No. 2 of the wood-cut, Strophomena deltoidea, and of the Reports, is an exceed¬ 
ingly abundant fossil in this rock; and as far as a knowledge of its range has been acquired 
either in this State or elsewhere, it is restricted to it, and is therefore a characteristic fossil. 
It is in greatest number at Trenton falls, and the range generally of this limestone in Oneida 
county. 
In a work like that of the survey of a State, where the object is to diffuse knowledge 
amongst the many, and not to the few only, a departure from common usage, where the 
obvious tendency was exclusive, should be made, be it ever so venerable from age, provided 
that the subject thereby is rendered simple and easy to be acquired. To attain this object, 
the specific name of the fossils will precede the generic ones as in our common language, 
and for the reason that the name of the species is more frequently used than that of the genus. 
The name, in all cases where new or doubtful, will be taken from the rock or group where it 
exists, or a locality equally characteristic. All received specific names will be rendered in 
the common language, as Deltoid strophoviena for No. 2 of the wood-cut, no change what¬ 
ever being made in those of the genera. 
No. 3. The Puffball favosite (Favosites lycopodites), from its resemblance to that common 
fungus, is also highly characteristic, and is in great numbers ; but it is found also in the lower 
part of the Utica slate, where it ends. It is one mass of small angular cells, arranged side 
