74 TRANSACTIONS OF THE [DEc. 16, 
The lowest beds of the type section are seen just below the 
milldam at Trenton Falls village. In general the lower portion 
of the formation is most shaly and is inclined to be nodular, but 
the limestone increases in purity and becomes crystalline in 
the higher layers. With the exception of the gray crystalline 
heavy beds in the upper part cf the mass, the layers rarely ex- 
ceed one foot in thickness and are usually two to six inches 
thick, separated by more shaly layers. As these thin layers 
vary in hardness they weather at different rates, affording indi- 
vidual prominence. There are, however, several conspicuous 
seams of hard, dense, blue-black limestone, several feet thick, 
which continue very constant and therefore form excellent da- 
tum levels for measuring up the section. 
The walls rise a hundred feet or more high, throughout the 
length of the gorge; and in spite of local variations of dip, the 
conspicuous seams may be traced uninterruptedly along the 
cliffs. One such seam is used for reference in locating the thin- 
ner layers until it is cut off by one of the water falls, when we 
may ascend to a higher level above the fall and there take bear- 
ings by an overlying heavy bed. These occasional heavy beds 
of pure limestone furnish the most perfectly preserved speci- 
mens of Asaphus platycephalus, for which the Trenton Falls 
locality is noted. Local collectors inform me that the entire 
specimens are usually found lying in the rock with ventral sur- 
face uppermost. 
These conspicuous datum layers are shown in the accompany- 
ing photographs: Plate II, showing the heavy bands in Sher- 
man Fall; Plate IV, figure A, a nearer view of one of the blue- 
black seams (D 11) just above the same fall. 
Measured in this way the following results were obtained, 
here presented in the order in which they were observed, namely, 
from below upward.* 
The specific faunal determinations are based on a rapid study 
and may need revision with more detailed work. They are, 
however, sufliciently correct for their intended purpose of es- 
tablishing the general character of the faune of the various 
zones. 
I. TRENTON FALLS SecTION—130C+D. 
Trenton Falls village bridge to Prospect bridge along Kauya 
Hoora gorge. 
* NorE.—The order of names in the faunal lists represents approximately the abun- 
dance of the yarious species, the most abundant being placed first, and if especially 
numerous designated @ (abundant), e (common), or conversely 7 (rare), etc. 
The measurements in the right-hand margin show the height of the top of the layer 
above the base of the section. The thickness of any layer may then be readily seen by 
subtraction. 
