THE EURYPTERIDA OF NEW YORK 351 
individual, the lateral margins converge but slightly forward; the anterior 
angles formed by the projecting eyes and the anterior margin being well 
rounded. In mature carapaces the lateral and anterior margins are less 
rounded and more nearly straight, the lateral margins subparallel. The 
posterior edge is slightly incurved. The surface is very gently convex, 
and seems to have been originally rather uniformly, but very moderately, 
elevated with a slight depression along the medio-anterior margin of the 
compound eyes. The latter are subelliptic, very prominent, project beyond 
the margin of the carapace and are located at the antelateral angle of 
the cephalothorax. Their length is nearly one half that of the lateral 
margin of the cephalothorax; their distance from each other is distinctly 
less than the length of the eye. As more fully stated in the generic 
description, the compound eyes are entirely smooth in their exterior 
view, the facets becoming visible only when the exterior layer of 
the cornea has become split off or on an interior view. The facets 
are small and squarish in shape. The ocelli are borne on a small 
oblong or rhomboidal tumescence, situated in a line connecting the bases 
of the marginal eves, and sometimes prolonged posteriorly in a crest. 
The ornamentation consists of an extremely fine granulation evenly dis- 
tributed over the carapace, becoming coarse between the compound eyes. 
A relatively narrow doublure surrounds with uniform width the frontal 
and lateral margins of the cephalothorax. The doublure at the base of 
this shield is three times as wide; it follows the entire posterior margin, 
thus making the doublure ring complete. 
Abdomen. The abdomen widens to the third or fourth dorsal seg- 
ments, where, in mature individuals, it seems to have been wider by one 
fourth than the base of the cephalothorax. From this point it tapers 
very gradually to the telson. 
Preabdomen. ‘The first of the six tergites is shorter by one half than 
the following ones. It is a narrow band, rather strongly curved forward 
in the middle portion and rounded at the ends. The following tergites 
are relatively broad, their length amounting to one third cf their width. 
