THE EURYPTERIDA OF NEW YORK 337 
segments are plain, bandlike rings, decreasing in breadth backward. In 
the first the breadth is considerably greater than the length; in the last, 
or penultimate body segment the length and breadth, in compressed speci- 
mens, are equal. The anterior end of each of these segments is marked 
by a groove for the attachment of the interarticular membrane. 
The telson is very slenderly lanceolate, widest near the anterior end 
and attenuated at the tip. In length it is equal to the four preceding 
segments. The dorsal surface is convex, rising from sharp, lateral edges 
to a median longitudinal carina, which begins in the anterior part as a 
_ broad, angular prominence; the ventral surface is nearly flat or faintly 
convex; a cross section is thus subtriangular. Compression usually flattens 
the sides and thus heightens the angular appearance. The uncompressed 
specimen has a length of 31 mm and a greatest breadth of 7 mm. 
On the ventral surface of the cephalothorax, in front, is a convex 
lobe or platform, the epzstoma, from which extends a flat, tapering doub- 
lure ending in a small expansion at the genal angles. In molting and also 
from compression, the epistoma divided through the middle rather than 
along the sides. 
Appendages. The preoral appendages are short, stout, three-jointed, 
chelate organs attached at the posterior border of the epistoma. The 
two distal joints of each form a pair of broad based, edentulous, bevel- 
edge pincers, in the ordinary state of compression having a breadth 
equal to one half the length. The blades are about equal in length 
to the basal portion and meet at the very acute, slightly curved tips and 
again, usually, only near the base. There is considerable variation in 
the relative form of the pincers, as shown on plate 11. The broad basal 
joints are about one fourth longer than the pincers, widest near the base - 
and longest on the inner side, and in the natural position extend beyond 
the anterior margin of the shield for about one third their length. The 
pincers articulate with this joint in such a way that, when folded back- 
ward, they cross it obliquely, and their tips converge a little in front of 
the mouth; when extended forward, they diverge somewhat. The preoral 
appendages could also be turned back to their full length over the mouth, 
the pincer tips then overlapping the metastoma. In an individual having 
a cephalothorax 22 mm long, the preoral appendages are 1o mm long. 
The four pairs of endognathites, or crawling legs, do not differ materially 
from one another except in length. The anterior limbs are somewhat 
shorter than the extended preoral appendages, and their tips extend but 
very little beyond the margin of the shield. Each succeeding pair is about 
one half longer than the preceding, so that the last limbs are probably four 
times as long as the first. All have seven joints, of which the terminal 
is spinitorm. The third to the sixth joints inclusive carry ventrally and 
at the distal ends a pair of striated, slightly curved, slender spines. The 
