Page:The Eurypterida of New York Volume 1.pdf/77

 the articulation between the carapace and abdomen and that between abdomen and telson, and the spiniform telson.

The other marine animals that have been repeatedly referred to as indicating the habits of the eurypterids by their similar swimming feet are the crabs of the family Portunidae, notably Matuta and Portunus (Huxley and Salter),  (Hall), and Portunus (Laurie). Our most common forms with swimming legs are the edible or blue crab and the lady crab. Here the question arises as to whether their last pair of limbs which so strongly resemble the swimming legs of many eurypterids, are better adapted to swimming or to digging. A full account of the habits of  has been given by Mary J. Rathbun, and a shorter account of the habits of the edible, lady and green  crabs by Paulmier. We learn from these descriptions that the edible crab usually wanders about crawling or hides under stones and logs and in seaweeds, but when pursued and finding speed ineffective, will rapidly bury itself in the sand to escape observation. As October draws to a close the crab moves into deep water and at this season may frequently be seen paddling near the surface as he works himself down stream with the tide. Paulmier states that "as may be supposed from the finlike posterior legs, it is a good swimmer and may often be found at the surface." On the other hand, he says of the lady crab, which has quite similar swimming legs: "Its usual habitat is the sandy beaches, even the most exposed, when at low water mark it buries itself all but the eyes and antennae and is on the watch for enemies and prey. If disturbed when feeding or if dug out, it disappears with great rapidity, burrowing backward into the sand."

We thus infer, and have verified this inference by actual observation, that they use their last legs with great ease for both digging and swimming, but are more given to a crawling and a burrowing than to a swimming habit.