in the specimen is distinctly outlined by its chitinous section. Their length is but one sixth that of the carapace. They lie a little in front of the middle of the carapace and about four times their width from the lateral margin.
The preabdomen is the broadest part of the body, broader by one fourth than it is long. Its sides are subparallel, as it increases but little in breadth to the fourth tergite, and then decreases again. The lateral margins of each tergite converge anteriorly so that the postlateral angles project along the sides. The first tergite is only half as long as the others. Its lateral portions are produced forward into flat lobes, as they are also in the next tergite, while in the following two the anterior margins are nearly straight and in the last two they are gently convex forward. The first tergite is entirely flat and smooth, the following are slightly raised in the middle portions of the posterior belt and culminate in a round median node highest on the third tergite and obscure on the last.
Of the postabdomen three segments and a portion of the fourth are shown. The first is of similar width and shape as the last tergite but furnished with long, striated spines at the postlateral angles, as are also the following postabdominal segments. The second segment is but half as wide as the first, but longer by one third. Its epimera are drawn out into long, slightly curved, oblique, posteriorly directed spurs. The last segment fully exposed is again longer and carries a still longer spur on the side.
The third postoral appendage is preserved nearly entire. It was short and stout. Impressions of spines appear on one of the segments. Of the fourth limb five slender segments are shown, so that this is probably also entire. Of the last limb, the five short basal segments, following the coxa are exposed. The other side also retained portions of the last two segments which were long and formed a paddle as in Eurypterus and Pterygotus. The specimen also retains the second limb which is a short stout walking leg ending in a spine.
The impressions of the coxae of the swimming legs, figured by Meek and Worthen, are also faintly seen in this specimen. So also are im-
