JEFFERSON COUNTY. 
389 
There are two other masses insulated much in the same way. Thus, crossing from the 
bay at Sacket’s-Harbor, over to Pillar point, we again come upon the trenton, which extends 
over to the west side, or to Chamont bay. Here again the trenton is excavated deeply ; and 
after crossing the neck of Chamont bay, we find the shores consisting of the trenton, as far 
as Cape Vincent. 
From these remarks, the geographical extent of the trenton will be seen ; and in the details, 
I have introduced those facts which relate to the causes which have controlled the present 
extent and limits of this rock, from which it appears that it has been considerably limited, 
especially in the part which extended north. 
I shall now proceed to speak of the fossils which characterize the trenton limestone. And 
upon this subject I may remark, that few rocks are so finely distinguished as this ; from the 
birdseye to the utica slate, it is not only well supplied with organic bodies, but they are 
limited to this mass, so far at least as it has been examined in New-York. Not one of the 
fossils of the trenton have been found in the limestones below, and as yet it is quite doubtful 
whether they appear higher in the utica slate or loraine shales. Those which first claim our 
attention are the crustaceans, some of which figure largely in the fossils of the trenton rock, 
being found in great numbers wherever it occurs. 
3 1 
1. Isotelus gigas. 2. Strophomena deltoidea. 3. Favcsites lycopodites. 
The Isotelus gigas (No. 1), is one of the most persistent fossils of this mass. It, however, 
happens generally, that it is only obtained in parts, the extremities being very liable to sepa¬ 
rate from the body. It may be found at Essex, Plattsburgh, Chazy, Glen’s-Falls and Water- 
town. Some large individuals have been obtained near Glen’s-Falls, and in the shaly lime¬ 
stone at Plattsburgh. 
