THE EURYPTERIDA OF NEW YORK 373 
the fact that the European species P. bilobus, P.anglicus 
and P. barrandei, which possess similar rounded free rami and 
have afforded the entire chelicerae, also demonstrate that the fixed ramus is 
correspondingly formed, and that these characters of the chelicerae appear 
even in younger individuals. We insert here a sketch of the chelicera of 
P. barrandei, whose free ramus possesses the greatest similarity to 
that of our type, in order to show the probable form of the entire cheli- 
cera of P. cobbi. 
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Figure 79 Pterygotus barrandei Semper, here introduced for comparison. 
Natural size. (From Seeman) 
The second suggestion, above advanced, that P. cobbi may be 
only a variety, is also refuted by the evidence from the European material, 
which demonstrates that the chelicerae are very good indicators of speci- 
fic distinction. The chelicerae of the P. buffaloensis-mac- 
rophthalmus group are almost identical with those of P. bohe- 
micus Barrande, while those of the associated P.cobbi correspond 
closely to those of P. barrandei Semper, found with bohemicus 
in the Bohemian Upper Siluric stage. 
