No. 275.J 
295 
The principal quarries of the Seneca limestone are those of McAllis- 
ter, Rorison, and one belonging to the county adjoining the latter; half 
a mile south of the last is another extensive quarry, and also one half a 
mile southwest of the Canoga spring. The stone is quarried for build- 
ings and enclosures as well as for burning into lime. The layers do 
not generally exceed a foot in thickness, and are separated by thin 
seams of shale. From six to eight courses of the stone are to be seen 
in each quarry; each course is generally separated by thin seams of 
shale, and sometimes by a layer of hornstone; two or three of the latter 
sometimes occur in the same quarry, separating the courses of limestone. 
The hornstone is more commonly in courses of nodules in the limestone, 
sometimes one and at other times several courses occurring in the same 
strata of the different quarries. When dressed with the chisel it forms 
an elegant and durable material for stepstones, door and window caps 
and sills. 
The Seneca limestone is succeeded by a, group of shales of great thick- 
ness, and limited above by a thin mass of limestone, (the Tully lime- 
stone.) The group consists of several distinct members possessing cha- 
racteristic lithological and fossil characters. Most of the rocks of the 
group are highly fossiliferous, containing abundance of shells and co- 
rallines, with three genera and four or more species of trilobites. The 
different members of the group succeed each other in the following or- 
der: 
I. Marcellus shales. The northern boundary of theses shales follows 
the irregular line noticed as the southern limit of the Seneca limestone, 
extending across the county from near Canoga to Waterloo, and crop- 
ping out at numerous points along the roads and in the small ravines. 
The lower part is black and slaty, containing limestone in nodules or 
concretions, and sometimes in continuous strata having a concretionary 
structure. The fossils are Posidonia, a large spiral univalve, Pleuroto- 
maria 1 a spinous Leptaena or Strophomena, like the Leptaena spinulo- 
sa, with Orthis of two or more species. 
The concretionary strata of limestone, apparently result in the same 
manner as the nodular concretions; in the former case the quantity of 
material being sufficient to form a continuous stratum. The concre- 
tionary structure and seams of crystalline matter, pervade the whole 
mass, as in the septaria; and petroleum or liquid bitumen likewise oc- 
curs in the cavities, with a fluid of a light blue colour, resembling Prus- 
sian blue. The same substance was noticed in the cavities of septaria 
on Cayuga lake, and is mentioned in Mr. Vanuxem's report. 
