232 NEW YORK STATE MUSEUM 
As minor characters which, however, also contribute to give Eusarcus 
its peculiar or even odd appearance and which seem to be present in all 
the species before cited, may be mentioned the strong development of 
the spines of the walking legs, the relatively great length of the seventh 
segment of the swimming legs and the peculiar surface sculpture, which in 
all representatives shows a strong tendency to become tuberculate instead 
of triangular-scaly as in the others, i.e. the scales are much smaller, more 
crowded and more or less circular in outline. 
Three of the generic characters are closely correlated and combined. 
They indicate an attitude of the animal wholly different from that of 
Eurypterus. These are the triangular carapace, the frontal position of 
the compound eyes and the predominant size of the anterior walking legs. 
These characters demonstrate that Eusarcus raised the eyebearing front 
end of its carapace highest above the ground while Eurypterus brought its 
broad shovel-shaped frontal part down to the ground in walking. 
Another peculiarity is intimately connected with this style of bearing 
the carapace. Though at first glance it is apparently of minor importance, 
it gives species of Eusarcus a very different aspect from those of Euryp- 
terus and indicates a difference of habit in the two genera. In Eurypterus 
the walking legs are invariably bent backward 1in the fossil state, while in 
Eusarcus they are as invariably bent forward. In the hving animals 
their direction was downward in Eurypterus as well as in Eusarcus 
but while in the former the posterior spines are the longer, in Eusarcus 
the anterior ones were either longer or at least of equal length with the 
posterior. The greater length of the posterior row of spines in Eurypterus 
must have emphasized the effect of the greater length of the posterior 
legs in bringing the front of the carapace down and, likewise, the greater 
length of the anterior row in Eusarcus would have increased the effect of 
the greater length of the anterior legs and assisted in lifting up the front 
1 With the exception of the small Eusarcus obesus (probably a young 
form) while in the British Eusarcus scorpioides they are as strongly bent 
' forward as in our two species. 
