JEFFERSON COUNTY. 



393 



No. 3, is not uncommon in tlie sub-crystalline grey limestone of Watertown. The fossil 

 was furnished by Dr. Crawc, to whom I am indebted for many similar favors. 



No. 4. This is the only specimen which I have seen of this fossil. 



No. 5, is a beautiful bellerophon of Watertown, in the same crystalline limestone. 



No. 6. Bellerophon bilohatus. If this is the same fossil figured by Mr. Murchison in the 

 Silurian System, it furnishes an instance of a wider range than is possessed by the Trenton 

 fossils generally. It is not clear that it is the same, but the resemblance is so close that it 

 seems inexpedient to give it a new name. The fact that it occurs so far below tlie bilobatus, 

 is presumptive evidence that it may be different. This species is common at Watertown, and 

 it has been discovered by myself in Crown-Point, near the fortification. 



In all the older rocks, some difficulty is experienced in obtaining the important parts of the 

 fossils in a state sufficiently whole to enable the palceontologist to decide upon the question of 

 identity. In most instances, for example, the form of the mouth is lost in consequence of 

 the fracture of the lip. 



102. 



Nos. 2. and 3. Pleurotomaria lenticularis, already referred to. The drawings preserve the 

 character of the fossil more perfectly than in No. 2 (fig. 101). 



No. 1 . Pleurotomaria , is common at Watertown, in tlie grey variety of the trenton 



limestone. 



103. 



.S-- 



Nos. 1, 2, 3. Bellerophon profundus, is abundant in the black variety of the trenton. It is 

 found upon the banks of the river at Watertown, in the lumpy variety of this rock. It may 

 be obtained from certain irregular masses which no one would suspect to contain fossils ; the 

 masses arc black, smooth and poUshed, and exhibit no external markings. This fossil is some- 

 times found of a size three or four times larger than in the above drawings, which is that of the 

 individuals discovered in this locality. In none of these small specimens was I able to obtain 



Geol. 2d DisT. 50 



