THE EURYPTERIDA OF NEW YORK 299 
The body plate in this group is very narrow (76 mm) as compared 
to its length (23 mm). Its division into right and left halves by a suture, 
the arching of each half and the produced antelateral angles indicate it to 
have been a paired sternite. 
In the second group one of the imperfect arms consists of the four 
distal joints, the other of two imperfect proximal joints. The joints of 
the former are short and expanded at the articulations. The first and 
second are each provided on the posterior side with a pair of distally directed 
spines. These are long, curved and sharp like those of the large arm of 
the other group. The second has also, on the opposite side of the distal 
angle, a single, large one extending parallel with the axis of the arm. The 
penultimate is long and shows no sign of having been spiniferous. The 
terminal is about equal in length to the spines and, like the terminal appen- 
dage in the other group, is clawlike. This arm, judging from the shortness 
of the joints and the broadening at the articulations, probably corresponds 
to the second described from the other group. The joints of the other arm 
appear to correspond to part of joints two and three of the first of that group. 
Associated with this last, and lying partially beneath its larger end, 
is a fragment of test which is ornamented by sharp, triangular scales dif- 
fering from anything found on the other eurypterids herein described. 
However, it is not certain that this had any connection with this arm. 
Aside from this possibility, neither the appendages nor the sternite show 
any signs of ornamentation. 
The most noticeable features revealed by these specimens are: the 
_ robustness and the great difference in size of the several pairs of endogna- 
thites; on the anterior three of these the arrangement in pairs of the pos- 
terior spines, which, on the first two, are noticeable for their shortness 
and lanceolate form, and on the third for their length and curvature; the 
high degree of specialization of the fourth pair of endognathites, shown 
by the great length of the joints and the number and large size of the 
spines; the narrowness and proportionately great length of the compound 
sternite; and the probability of there being several compound sternites. 
It is evident that the animal had a long, slender body with long, very 
strong limbs. 
From a comparison of these parts with those of the various genera 
of eurypterids, it appears that they do not agree very closely with any. 
To show this, it is necessary only to point out certain of the more evident 
differences. In Eurypterus proper the fourth endognathite, to which I 
consider the longer of these arms to correspond. consists of nine joints, 
probably a greater number than is possessed by the other; besides, it bears 
no spines except the two formed by the prolongation of the eighth or 
penultimate joint. On the three anterior pairs of endognathites the spines 
are more uniform in shape and size. The body is proportionately broader 
