THE EURYPTERIDA OF NEW YORK 185 
of the body. Its surface was evenly and highly convex, culminating near 
the center at the ocellar mound. It is surrounded by a narrow thickened 
filiform border. The posterior margin is straight transverse with a faint 
indication of fulcra near the acute genal angles. 
The compound eyes are subcentral in position, situated as stated in 
the preliminary description; the visual surface is crescentic and only promi- 
nent in compressed specimens, while the entire ocular node, which has 
the form of a sector, being rounded at the outside and angular on the inner 
side, is distinct only in young individuals. The eyes occupy about one 
third the length of the carapace.' The ocelli are situated on a line con- 
necting the centers of the compound eyes and located on a large, promi- 
nent mound. 
Abdomen. The abdomen is slender, widening so little from the base 
of the carapace to the third segment that in many specimens it tapers 
with apparent regularity toward, the telson. The length is three times 
the greatest width. | 
The preabdomen is widest at the third and fourth tergites. Its 
length is to its width as 5:4. The tergites are narrow bands with 
straight or but slightly curved transverse margins and parallel lateral 
margins. ‘The anterior and posterior margins diverge near the lateral 
extremities where the segments widen somewhat. Their antelateral 
angles are produced into broad blunt lobes, while the postlateral angles 
are either rectangular or furnished with short acute lobes, that are directed 
posteriorly and increase somewhat in size in the posterior segments. The 
segments were originally highly arched with a narrow flat strip, represent- 
ing the epimera, along the lateral margins. Each tergite was not only 
strongly bent from one side to the other but also from forward back- 
ward and highest in the anterior third, with a steep decline forward 
and a more gradual one backward, finally grading into a narrow flat border. 
‘ The extreme variation in size and location of the compound eyes is due to different 
direction of compression and has been more fully described under ‘‘ Remarks.”’ 
