Page:The Eurypterida of New York Volume 1.pdf/433

 from the Frankfort beds at Schenectady and the still earlier  from the Normanskill shale at Catskill also exhibit median extensions of the frontal margin of the carapace similar to the frontal lappet of.

The compound eyes in  appear to be placed considerably farther inward than in. We do not know, however, how much this difference is due to the fact that in  the entire carapace is spread out, having been rather flat along the lateral margin, while in   the marginal parts were more or less vertical and bent under, thus bringing the submarginal lateral eyes on the margin of the compressed specimen. This latter condition is seen in the types of plates 29 and 30.

When investigating this genus we were unable to locate the types of the Pennsylvania Carbonic species described by C. E. Hall and James Hall. These have been found in the Hall collection of Chicago University, whence we were able to borrow them through the courtesy of Professor Stuart Weller. For the purposes of completeness and facility of reference some notes on the species are here given:

C. E. Hall. Am. Phil. Soc. Proc. Phila. 1877. 16: 621

James Hall. Sec. Pennsylvania Geol. Sur. PPP. 1884. p. 32, pl. 4, fig. 1–8; pl. 5, fig. 1–11; pl. 6, fig. 1; pl. 7, fig. 1; pl. 8, fig. 1–3

James Hall. Ibid. p. 34, pl. 5, fig. 12–15

Cf. James Hall. Ibid. p. 37, pl. 4, fig. 9, 10

and  are associated in the "shale immediately below the Darlington cannel coal, near Cannelton, Darlington township, Beaver county, Pennsylvania." Hall cites [ op. cit. p. 35] as the distinguishing feature of  and