A4 NEW YORK STATE MUSEUM 
ever, were relatively large and had stronger chelae. The specimen 
of E. scorpionis reproduced on plate 32, retains them in their 
natural position. Woodward figured them, as pointed out by Laurie, in 
Eurypterus scorpioides, whichis an Eusarcus. In Dolichop- 
terus and Drepanopterus they are not known. In general it may, how- 
ever, be said that they were extremely similar in the genera of the 
Eurypterus group, viz, Eurypterus, Eusarcus and Stylonurus. 
On the other hand they show extreme variation in the genera of the 
Pterygotus group, viz, Hughmilleria, Slimonia’ and Pterygotus. In Shi- 
monia they were discovered by Laurie [1893, p. 511, pl. 1, fig. 3] and found 
to be very small and with strong curved pincers, but otherwise as in 
Limulus. Those of Hughmilleria have been fully described by Sarle. 
They are larger [pl. 61, fig. 6] than in any other genus except Ptery- 
gotus, projecting beyond the margin of the carapace when extended and 
thus forming a transition to their condition in the latter genus. In Ptery- 
gotus they have been developed into the gigantic pincers which give that 
genus its fantastic aspect. Notwithstanding their great size in Pterygotus, 
there still prevails much doubt as to their structure. The current resto- 
ration [Zittel-Eastman’s Textbook, fig. 1423] is one that would indicate 
a structure greatly different from that of the chelicerae of the other 
curypterids. Our material fortunately sheds light on this problem and 
we have for this reason inserted here the following note. 
The morphology and formation of the chelicerae in Pterygotus. 
In several specimensof P. macrophthalmus and P. buffalo- 
ensis at our disposal, the chelicerae are so excellently preserved as to 
remove all doubt regarding their morphology and function. In one 
[pl. 74, fig.1 ] the chelicera of a large individual is perfectly preserved 
from the distal extremity of the chelae or pincers to the base of attach- 
ment. This shows distinctly that the organ consisted only of one un- 
jointed long arm carrying the terminal pincers. In the second specimen 
the arms of both chelicerae lie side by side, while the pincers of both have 
swung back, one until it is subparallel with the arm. These latter chel- 
