Page:The Eurypterida of New York Volume 1.pdf/292

 The genotype is not sufficiently known to establish its relationship to any of the three subdivisions here proposed.

Subgenus A is typically represented by  and. 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. Laurie also belongs in this group.

We suspect that also, 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, whicht 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  Laurie and   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,, only known from two of its legs, clearly belongs here; and we surmise that   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