WATERLIME GROUP. 
383 
GEOLOGICAL POSITION AND GEOGRAPHICAL DISTRIBUTION OF THE 
AMERICAN SPECIES OF EURYPTERUS. 
The true geological position of the rocks containing Eurypterus in this 
country is well determined in the series ; and in order to present its 
relations the more clearly, I give below the names of several groups in 
their order, that the sequence may be seen without referring to any other 
table of formations. 
Hamilton group. 
Upper Helderberg limestones, 
including Schoharie grit. 
Caudagalli grit. 
Oriskany sandstone. 
Upper Pentamerus limestone; 
Encrinal limestone. 
Shaly limestone. 
Lower Pentamerus limestone; 
StROMATOPORA LIMESTONE; 
Tentaculite limestone. 
WATERLIME GROUP . . . . < 
Onondaga-salt group. 
Niagara group. 
This series is found full and unbroken in the central part of the State 
of New-York, as in Oneida county, where the Eurypterus beds containing 
E. remipes, etc. are easily traceable passing beneath the Tentaculite lime¬ 
stone ; while in Western New-York, and in the locality where E. lacustris 
occurs, the strata of the Lower Helderberg group are absent, and the 
beds bearing these fossils, together with Pterygotus and Ceratiocaris , pass 
directly beneath the limestones of the Upper Helderberg group which 
contain the remains of fishes. In the absence, therefore, of that very im¬ 
portant group of strata, the Lower Helderberg limestones, the Eurypterus 
might seem to belong to the uppermost Silurian rocks of our country; 
while in fact, where the series is complete, the position of these fossils 
is beneath a well-marked and persistent group having intimate relations 
[ Paleontology III.J 49 
DEVONIAN. 
These constitute the limestones of the 
LOWER HELDERBERG GROUP. 
A single small carapace of a Eurypterus is 
J known from the Tentaculite limestone. 
Position of E. remipes, E. lacustris and others^ 
with Pterygotus and Ceratiocaris. 
