Page:The Eurypterida of New York Volume 1.pdf/219

 The lateral eyes are apparently reniform and not very large, about one fourth to one fifth the length of the head shield. They lie on the anterior half of the carapace, just in front of the bisecting transverse line. The ocelli have not been seen. The doublure of the carapace is very broad in front, about one ninth the length of the head, narrowing somewhat posteriorly, distinctly produced in the median line to form a small triangular shield.

The abdomen is little wider than the carapace, the preabdomen as wide as long, and the postabdomen relatively short and compact, longer by one third than the preabdomen. The tergites are short, the length about one sixth of the width, with broadly concave posterior margins in the middle half. The sternites are longer (length : width as 1 : 4.5), the operculum apparently but little different from the other sternites in size and outline. In compressed specimens their anterior margins are almost straight. The doublure is apparently narrow. The posterior margins are deeply concave in the middle portion and project into broad, rounded lobes at the lateral angles. The doublure widens under these lobes so that its anterior margin is approximately transverse. All sternites bear transverse oval gill plates whose major diameter is twice the minor. Those of the operculum are but half the size of the others and those on the last pair of sternites are smaller. The postabdominal segments gradually increase in length posteriorly, the last being twice as long as the first, but only one third as wide. The posterior doublure is narrow (1.5 mm). The last segment is produced at the postlateral angles into two short broad lobes with blunt extremities. The telson is short and thick, a little more than one fifth the length of the body. It contracts very rapidly in its first third, then more gradually to its blunt extremity.

Appendages. Only four pairs of limbs have been observed, viz, the three last pairs of walking legs and the swimming legs. The walking legs, notably the last pair, are relatively a little stronger than those of most other members of the genus, while the swimming legs are slender and bear a long terminal spine in place of the "claw," thereby indicating their