THE EURYPTERIDA OF NEW YORK 343 
posterior edge is very gently concave forward, nearly straight. The dorsal, 
surface was uniformly and strongly convex, culminating between 
the lateral eyes and somewhat impending along the sides. A narrow 
flat border surrounds the lateral and frontal margins. The compound eyes 
are of medium size (one fourth to one fifth of length of carapace), intra- 
marginal in position, separated from the margin by an interval nearly 
as wide as the eyes themselves. On account of the position of the eyes 
on the impending sides of the carapace, however, they appear in most 
compressed specimens to be marginal [pl. 64, fig. 13; pl. 65, figs. 1, 6,9]. 
They are placed so far forward that they are distant only their own length 
from the foremost point of the carapace. The form of the ocular node 
resembles that of an elliptic sector, the outer margin being rounded and the 
inner margin angular or composed of two, frequently unequal radu, the 
anterior being the longer. The anterior end of the node is acute, the 
posterior rounded. The node is so slightly prominent that the eyes 
hardly project beyond the outline of the carapace. The visual surface 
is crescentlike with somewhat swollen extremities [pl. 65, fig. ro] and 
situated along the outer edge of the ocular node. The ocelli are dis- 
tinct, separated by the length of their own diameter, and situated on a 
flat circular tumescence that lies on a line connecting the inner angles of 
the compound eyes. 
Abdomen. The abdomen is slender, increases slightly in width to the 
fourth dorsal. segment and then tapers very gradually to the telson. Its 
greatest width is about one fourth the length of the body. 
_ Preabdomen. The tergites [pl. 66, figs. 6, 8, 11] are narrow, sub- 
rectangular bands with anterior and posterior margins straight or but 
slightly bent forward, three to four times as wide as long, save the first 
which is six and one half times wider than long, or in other words, is a very 
narrow band. The anterior edge of the latter is straight, the posterior 
gently concave. The antelateral angles are broadly rounded and pro- 
duced forward and the postlateral angles slightly extended posteriorly 
so that both extremities of this segment are widened. In the following 
