286 NEW YORK STATE MUSEUM 
The genotype is not sufficiently known to establish its relationship 
to any of the three subdivisions here proposed. 
Subgenus A is typically represented by S. logani and S. mac- 
rophthalmus. Its first three pairs of legs retain the characters of 
those of Drepanopterus and are like those of Eurypterus, i. e. relatively 
short and stout and furnished with two curved, strong spines on each 
segment. S. ornatus Laurie also belongs in this group. 
We suspect that also Eurypterus scabrosus, a curious 
form described by Woodward [1887, p. 481] from the Lower Carbonic 
shales of Eskdale, belongs here, although the specimen does not retain the 
fifth pair of legs, which are of critical importance in the distinction of 
Eurypterus from Stylonurus.: The great length and slenderness of the 
preceding legs, however, are a character only found in Stylonurus, but 
not in any of the species of Eurypterus known to us. Likewise the coarse, 
roundish, tuberculate sculpture of the posterior margins of the tergites is 
more suggestive of Stylonurus than of Eurypterus. | 
Subgenus B. This is typically represented by S. elegans Laurie 
and S. cestrotus Clarke. Its second and third pairs of legs are 
relatively much longer and furnished with more than two pairs of long, | 
less curved spines which are vertical on the lower side of the segments. 
Besides the species mentioned, another form from the Pittsford shale, 
S.multispinosus, only known from two of its legs, clearly belongs 
here; and we surmise that S. excelsior also, from the character of 
its first legs which alone are known, should be brought under this group. 
In case this structure should not be found in Stylonurus proper, the 
1 Woodward refers this form unhesitatingly to Eurypterus, stating in regard to the 
fifth pair of legs [p. 483]: ‘‘ The fifth pair of broad spatulate swimming feet answering 
to the maxillae, or to the maxillipeds of the higher Crustacea, are not preserved in this 
fossil; but as they have been found with nearly all the species of Eurypterus hitherto 
described, there is little doubt that this form also possessed them when entire. Certainly 
the other appendages reproduce with only slight modification in their style of ornamen- 
tation those of the Russian, the American and the Lanarkshire Eurypteri already de- 
‘scribed and figured by Hall, Schmidt and myself.” 
