Page:The Eurypterida of New York Volume 1.pdf/81

 shoveling edge, the dorsal or subapical position of the lateral eyes, as in Limulus, which would allow them to project above the mud, the peculiarly long, mobile and yet strong articulation of the carapace and first body segment, and the spiniform telson.

It has been particularly pointed out by Holm [ op. cit. p. 9] that in  the articulation between the carapace and the preabdomen must have been one of great mobility, as indicated by the broad slit, closed only by a membrane between the lateral fulcra. This connection was nevertheless so strong that the first preabdominal segment is most frequently found attached to the carapace in dismembered specimens. These facts suggest that Eurypterus may have been able to use the articulation between the carapace and the abdomen somewhat like Limulus in pushing itself through the mud, a process which would be aided by the tail spine.

On the other hand, there is good evidence that the species of Eurypterus were able swimmers. We have elsewhere cited Holm's description of the adaptation of the swimming legs in, evident in the sharp anterior keel of the organ and the arrangement of the articulation allowing the turning of the oar blade into a vertical position. Still more conclusive is the preceding pair of spineless slender legs, which would seem to have no other function than to serve as balancers and aid in swimming.

The combined evidence of the characters of Eurypterus is that it was a still little specialized, primitive genus, not yet wholly adapted to either crawling, digging or swimming, but could perform all these functions and was on the whole a sluggish animal. As it is not provided with strong organs of offense, it probably lived on worms or carrion.

There are certain species of this genus, such as, which are distinguished by a remarkably slender form. As a rule these also have the eyes far forward on the small carapace. Their form indicates that they were more inclined to a swimming habit. Others have the broad head of a catfish and seem well adapted to resting on the mud and there