384 NEW YORK STATE MUSEUM 
Plate 87, figure 9 represents a fragment of a large tergite with traces 
of the Pterygotus ornamentation. This can be referred to P. proli- 
ficus with some certainty. 
Characteristic telsons of Pterygotus [pl. 87, fig. 5, 7] are not infrequent 
at Schenectady and Duanesburg. A very different type is represented by 
plate 84, figure 8. It exhibits a peculiar ornamentation, consisting of 
small groups of tubercles on low nodes arranged in subconcentric lines; 
the other side was smooth. The serration of the margin is very distinct 
and shows by its direction that the small incision on the longer side is the 
middle of the posterior margin of the telson and is a faint beginning of 
the bilobation characteristic of Erettopterus. 
Plate 87, figure 6 illustrates a form of fragments met with repeatedly 
in the beds at Schenectady, and quite obviously a last postabdominal 
segment best comparable to that of a Pterygotus. 
Finally, these black shales also contain small patches of integument 
which retain the surface sculpture in a preservation surpassing any 
hitherto observed in our eurypterid-bearing rocks. Some of these patches 
[see pl. 86, fig. 11-15] are clearly referable to Pterygotus.' 
1 Disjecta membra from the Frankfort shale, not referable to any genus. 
Besides the few parts of the integument referred in the preceding descriptions to genera 
known from the Upper Siluric and Devonic, a considerable number of fragments have been found 
which cannot be placed with any degree of certainty with any of the genera; some are of non- 
committal character, while others differ so strikingly from all later forms that they undoubtedly 
represent new types of greater than specific rank and must await future discoveries of more com- 
plete material, for description. We merely figure these here to indicate the richness of this new 
eurypterid fauna, 
Plate 86, figure 18, is a coxa, possibly belonging to Pterygotus; plate 84, figure 17, the greater 
part of a broad, rapidly contracting abdomen, possibly belonging to Eusarcus, and plate 84, figure 
19, a long, extremely slender, distinctly striated spine, suggesting Dolichopterus and Stylonurus, 
Most indicative of the great diversity of forms occurring in the Frankfort beds are the well 
preserved patches of integument found in the black shale. Some of these have been mentioned in 
connection with the genera Eurypterusand Pterygotus. We figure here several patches bearing the 
ormamentation described of Eusarcus, Echinognathus and Megalograptus and exhibiting some 
variations [pl. 84, fig. 13-16]. Another style of ornamentation is represented by figure 8 of plate 83. 
This consists of extremely fine, very closely and evenly arranged tubercles. The patch of integu- 
ment, reproduced in plate 85, figure 8, shows a mass of densely set, short, sharp spines and that 
shown in plate 85, figure 7, a profusion of long slender spines. 
Plate 85, figure 10, isa part of a supposed leg segment with a strange pattern of parallel raised 
lines connected by another set of shorter parallel oblique lines, | 
