Page:The Eurypterida of New York Volume 1.pdf/172

 third longer than wide, distinctly convex forward and furnished with a small spine at the posterior end of the gently concave distal margin. The fifth segment is subquadrate, deeply emarginate at the under side of the distal extremity [ pl. 7, fig. 8] and furnished with a triangular process on the upper side. The sixth segment is semioval, rapidly expanding distally and bearing an acute articulating process on the distal extremity. The seventh and eighth segments are much expanded; the seventh subrectangular, its anterior side very convex, the posterior nearly straight. The triangular guard plate is of relatively large size, its distal margin finely serrate. The eighth segment is oval in outline, about as long as the seventh, but only half as wide. Its anterior margin is very finely serrate, the serrae becoming longer and narrower toward the extremity and grouped into larger serrae, alternating with about six small ones [ pl. 7, fig. 11]. The latter segment bears the small, oval, rudimentary ninth segment.

The epicoxite has not been seen in position; a detached epicoxite, found in association with this species and presumably belonging to it, is reproduced on plate 7, figure 5.

The endostoma has not been seen.

The metastoma is oval, not quite twice as long as wide, widest in the middle, or a little in front of the middle. The anterior extremity is gently emarginate and the posterior truncate.

The genital appendages of the species have been found well developed in but very few specimens, obviously owing to the fact that the great majority of individuals in the Litchfield region are immature. A mature female operculum with appendages, except for the terminal pair, is shown in plate 8, figure 1. The most important features of this specimen are the two pentagonal anterior pieces separated by sutures from the two halves of the operculum, and the two imbricating unpaired lobes, each of which expands slightly at the posterior extremity and terminates with two diverging, acute lateral lobes. The two tubular organs which were first recognized by Holm in, are here seen as two black