Fig. 105-7 Fragments of Pterygotidae. Fig. 105 Swimming leg. × 2. Fig. 106 Telson of a true Pterygotus. Fig. 107 Probably of an Erettopterus. Both × 2
is also attested by telsons, some of which indicate a true Pterygotus [see text fig. 106] while others suggest forms of Erettopterus [see text fig. 107]. We also figure with these a swimming leg, possibly belonging to this group.
EURYPTERIDS FROM THE SHAWANGUNK GRIT IN PENNSYLVANIA
On a previous page [87] reference is made to the occurrence of obscure eurypterids in the Shawangunk grit of the Delaware Water Gap, Pennsylvania. The material we then had proved indeterminable, but since then through the courtesy of Professor Gilbert van Ingen we have had opportunity to examine a very large number of specimens from the same locality recently acquired by him and Mr J. C. Martin. In regard to the horizon Professor van Ingen writes:
These eurypterids are from the third quartzitic conglomerate, "Medina white conglomerate, no. 2" of section B, at Delaware Water Gap, which is published as plate I, 1882, Report G6 (Second Pennsylvania Geological Survey). They come from about the middle of this band, and occur in thin seams of black shale of very irregular extent horizontally and of variable thickness and character vertically. Some of the shale seams have none, others abound in the eurypterids.
It thus appears that the occurrence of the eurypterids at the Delaware Water Gap is the same as that in the Shawangunk grit at Otisville.
Unfortunately the maceration, already so prevalent in much of the eurypterid material at Otisville, has at the Delaware Water Gap reached such a destructive degree that the shale is filled with a mass of comminuted eurypterid fragments; and to complete the destruction the chitinous substance has also been chemically altered until it has a slickensided and silky appearance and for the greater part has lost all trace of sculpture. Owing to this extremely unfavorable condition of the material, only a few small carapaces and patches of integument warrant description, although
