THE EURYPTERIDA OF NEW YORK 249 
to be inferred from the relative smaller length of the preabdomen that 
the preabdominal plates were also relatively shorter. The first tergite 
would, from. the evidence of the largest specimen, seem to have been at 
least eight times as wide as long. The posterior margins (which alone 
are seen owing to the more abrupt termination) are nearly straight in the 
anterior tergites but become distinctly concave in the middle of the last 
two plates; in the sternites they are throughout broadly concave in the 
middle and well rounded at the postlateral angles. 
The gill plates are distinctly outlined in the smallest of the specimens 
[pl. 37,] and are of elongate, sublanceolate outline, rounded on the inner 
side and acutely pointed on the outer, sightly diminishing in size posteriorly. 
The postabdomen appears disproportionately long; it is fully twice as 
long as the preabdomen. At the same time it is broader (one fourth as 
wide as long) than in other species and has altogether the appearance of 
a very powerful organ. The first segment completes the contraction of 
the oval portion of the abdomen as in the other Eusarci, thence the post- 
abdomen is of nearly uniform width, contracting but one sixth to the 
posterior extremity. The first segment is a narrow ring with a strong 
forward bend, about four and one half times as wide as long. Thenext is of 
similar shape and rate of contraction, but four times as wideas long. At 
the postlateral angles it is slightly produced backward and its lateral mar- 
gins are concave, indicating that it had the form of a concave truncated 
cone. The next, like the following, is of tubular form. The last four seg- 
ments do not lengthen nearly as rapidly in this species as in Eusarcus 
scorpionis, the sixth being twice as long as the third and three fifths 
as wide as long. : 
The telson has been seen in but two specimens. In one of these 
it agrees with the figures given by Claypole of E. newlini and 
E. ingens in being short, stout and straight. Its length is one sixth 
that of the body and four times as great as its basal width. The basal 
fourth is slightly expanded or inflated, the remainder tapers regularly 
to a point. One of the specimens shows at the underside near the base a 
