ESSEX COUNTY. 277 



In the maclurca, the coursing of tlie lines, whicii are used in the shading of the figure, run 

 in the direction of the lines of the shell ; but almost the whole of the shell is naked, or in 

 other words, it is an inside cast, onl}'- a portion of the shell remaining near the mouth. So 

 far as any markings of the cast upon the outside appear, they do not indicate the existence of 

 septa or divisions similar to the naulilus; nor have I yet succeeded in finding a specimen 

 which exhibited any traces of a siphunculus. This interesting fossil is credited to Basin 

 harbor in Vermont, opposite Westport, and also to Eighteen-mile creek ; but the latter refe- 

 rence is undoubtedly a mistake, as this species is confined to the limestones below the tren- 

 ton, while the shales of Eighteen-mile creek belong to the Erie group. 



Equally limited is this species of columnaria : thus I have noticed it at Essex, Chazy, Isle 

 La Motte, Glen's-Falls and Watertown ; and at each of those places it occupies the position 

 I have given it, never appearing in the upper layers of the calciferous sandrock, nor in the 

 lower layers of the trenton limestone. I am not able to say that neither the raaclurea nor 

 columnaria ever occur in the birdseye limestone. Traces of a coiled shell similar to it appear 

 in a mass which resembles the birdseye at Chazy, but it is the only locality in the Second 

 district at which I find any traces of this fossil. 



This rock is about one hundred and thirty feet thick in the valley of Champlain. It does 

 not appear to be a constant mass, and 1 am disposed to believe that it does not exist in the 

 Mohawk valley, nor upon the Black river, wlicre the other limestones of the Champlain group 

 are so well developed. 



Trenton Limestone. 



This rock succeeds the chazy limestone in Essex county, the birdseye appearing to be ab- 

 sent. Upon this point, however, I do not speak positively : it may exist, as it does in one or 

 two instances in the Mohawk valley, in a very thin stratum, perhaps less than a foot in thick- 

 ness ; or if in thicker masses, very imperfectly developed, and with its specific characters 

 indistinctly revealed. 



The trenton limestone, though not in its usual force and thickness, vet is very well formed 

 and tolerably well characterized. At Essex village, as I have alreadj' had occasion to say, it 

 forms a mass forty or fifty feel thick, and is, as usual, a shaly rock, and filled with fossils, 

 particularly the Calymene senaria, in imperfect specimens by hundreds. A large species of 

 orthoceratite is also quite abundant, some of which are two feet long, but it is difficult to 

 obtain an entire individual. 



A locality two miles south of the village, is more important. The rock does not appear on 

 the roadside, but may be observed about half a mile west of Whallon's bay, in the meadows 

 upon a small stream which flows into the bay. The rock dips to the east, and is composed 

 of slaty layers alternating with those of a shaly limestone, in which fossils are numerous, 

 particularly the PuiTball favosite, several species of corallines, the Trinucleus tessellatus or 

 Tessellated trilobite, Calymene senaria, Orthis testudinaria, etc. It is not exposed, however, 

 to a great depth ; forty or fifty feet is all that can be seen. It is certainly the trenton lime- 

 stone, and is verj' clearly revealed by its fossils and lithological characters. 



