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THE EURYPTERIDA OF NEW YORK 213 
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 tri- 
angular 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 con- 
cave 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 pos- 
teriorly, 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 
