margins, while the succeeding segments have approximately straight transverse margins. The segments possess faintly outlined pleural areas denoted by a flattening of the lateral region, and a small spine on the postlateral angles. The spines of the last segment are distinguished from the others by their size, but do not grow into the long lobes which flank the telson in other species of Eurypterus. The posterior doublures are short, not one fourth as long as the segments.
The telson is short, having one fourth the length of the body, contracts rapidly from the articulation to one half its width and then continues slender to the bluntly triangular point. The margins are marked by oblique fine incisions that increase in size posteriorly and form a tuft of spines surrounding the point. The upper side is flat or slightly concave, the underside furnished with a rather narrow, flat-topped carina.
Appendages. The appendages of the cephalothorax with exception of the chelicerae were well known to Hall. They agree in all features with those of the closely related E. fischeri. The preoral appendages have been found more or less entangled with the endognathites; a single detached chelicera, lacking only the basal segment has however been observed [pl. 7, fig. 1]. The pair of pincers is broadest at the base, about twice as long as broad; the blades occupy only about one third of the length of the pincers; they are broadest at the base, taper rapidly, are edentulous, and with very acute tips. The tip of the movable blade is bent inward and is needlelike. The endognathites are relatively short and robust; of the first pair only the terminal spines or claws project beyond the shield border, while the members of the second pair extend for about one half their length beyond it, and those of the third pair clear it by fully three fourths their length. The fourth pair reaches beyond the third by the length of its last three segments. The first three pairs are of equal width, and in the first, the segments are twice as wide as long. The spines are long, slender, curved, paired and of subequal length, each segment bearing one pair [pl. 7, fig. 3]. The hooklike long, reflexed evagination of the fifth segment of the second endognathite in the male which has been
