Q2 NEW YORK STATE MUSEUM 
which are there obviously near the climax of their development. It is also 
the horizon where individual development is greatest.’ 
1Though we have been discussing the eurypterids of the Bertie waterlime as if 
they constituted a single congeries, there is actually a very marked geographic dis- 
tinction in their distribution. At the two productive localities, Erie county and 
Herkimer county, there are noteworthy distinctions in respect to species. The two 
faunules are as follows: 
HERKIMER COUNTY ERIE COUNTY 
Eurypterus remipes | Eurypterus lacustris 
Dolichopterus macrochirus E. lacustris var. pachychirus 
D. testudineus E. pustulosus 
Pterygotus macrophthalmus Eusarcus scorpionis 
P. cobbi Dolichopterus macrochirus 
D. siluriceps 
Pterygotus buffaloensis 
P. cobbi 
P. grandis 
The species common to both are Dolichopterus macrochirus 
and Pterygotus cobbi, both of which are quite rare, while the predominant 
species in both places are unlike. It is not believed that these differences necessarily 
express distinct stratigraphic horizons, as both congeries lie near the top of the water- 
lime succession, but rather indicate original regional separation into distinct lagoons 
or pools, so that we may without impropriety speak of these regions as the Buffalo 
pool and the Herkimer pool, which we may assume to have been synchronous. There 
is, in the face of the differences suggested, a certain degree of approximation in the 
two expressed by such vicarious species as E. remipes and lacustris, P. 
macrophthalmus and buffaloensis, which may well mean distinctions 
due to geographic isolation. The Herkimer pool is well restricted and its faunule 
can not be traced very far toward the west; the Buffalo E.lacustris, however, 
appears alone as far east as Union Springs, Cayuga co., andas far west as Bertie, Ontario. 
Another difference in these faunas is the preponderating great size of’ all the species 
in the Buffalo pool and, by contrast, the small size of and abundant young among the . 
Herkimer county species; a distinction which may be due to differencesindepth. That the 
smaller creatures lived in conditions of shallower water is evinced by the sun-dried 
and cracked rock surfaces of their matrix, while such evidences are wanting in the 
Buffalo pool; and indeed it would be quite in accordance with our acquaintance with 
