﻿82 NEW YORK STATE MUSEUM 



These species are not known to occur above or below the Low- 

 ville limestone, and are common enough to occur in every exposure 

 of the formation. 



Tetradium cellulosum forms large colonies, attain- 

 ing sometimes a diameter of several feet (specimens of this size 

 collected by the writer along Black river) and consisting of fre- 

 quently dividing branches that radiate horizontally and obliquely 

 upward from a common center. Its most characteristic aspect, 

 however, is seen on sections where the squarish cells with their 

 fission septa produce a neat lattice pattern. Different, hitherto 

 undescribed species with looser arrangement of the polyparies or 

 cells, occur in lower horizons. 



Both Orthoceras multicameratum and O. 

 recticameratum are easily recognized by the close ar- 

 rangement of their septa and the latter form possesses in the 

 angular course of the septa a character not shown by other 

 species. 



Bathyurus extans apparently occurs throughout the 

 formation but is most frequent in several bands. It is, as Dr 

 Ulrich informs us, preceded by closely related and very similar 

 prenuncial forms in the Pamelia formation. 



On account of the but slight difference in the compactness of 

 the rocks between the Lowville and Pamelia formations, the 

 former is not set off by an escarpment from the other, but both 

 form one continuous plateau. In some districts the lower Low- 

 ville contains easily worked layers, furnishing subciibical blocks 

 and the composition of the fences of such blocks is a quite char- 

 acteristic aspect for this horizon. 



Since the formation received its name from Lowville and a 

 section of this type locality has not yet been furnished, we insert 

 here the section, obtained at this place in the quarry at the railroad 

 bridge over Mill creek, where in the creek bank the uppermost 

 part of the Pamelia (about 12 feet) is shown and a continuous 

 section into the Leray limestone can (be obtained. On account of the 

 nearness of Lowville to the area here mapped, the Lowville section 

 is to be considered as typical also for this area. For comparison 

 we add the section measured in the Sanford out which contains 

 about three fourths of the formation. Another fine section was 

 observed in the bank of the Black river above Watertown, opposite 

 the filter plant, just outside the map limits, and a section of about 

 56 feet from the 7 foot tier downward is exposed in the high river 

 bank opposite the Ontario Paper mill, 2 miles east of Brownville. 



