of them is a young individual. Among the fragments are some that prove that this inelegant squatty eurypterid attained to similar gigantic proportions as the associated Pterygotus. The material at hand permits us to give a fairly complete description of both the dorsal and ventral aspects and of the various appendages.
Description. The outline of the body is a very broad oval, acute anteriorly and broadly rounded posteriorly, where a tubular tail (postabdomen) of equal length is affixed, ending in a long, curved telson, of again half the length of the tail.
Cephalothorax. The cephalothorax is about as broad as long, its outline is bluntly subtriangular, the two lateral margins converging at an angle of about 50° toward the anterior end which is truncated. The base is but little longer than the lateral margin (about one thirteenth). The anterior margin is about one third as long as the lateral margin. The posterior margin bends gently forward in the middle and is well rounded and projects slightly at the postlateral angles. The lateral margins were moderately convex; the frontal line slightly emarginate. There is evidence that the carapace was relatively convex along the middle axis and that it remained so to the anterior margin or even culminated there, where the compound eyes were borne on the sides of this frontal snoutlike prominence. The compound eyes are kidney-shaped, apparently smooth, without recognizable facets, about one tenth the length of the carapace and situated at the antelateral corners of the latter. The ocelli, well shown in one specimen, lie a little behind the center of the carapace [pl. 29], and probably occupied the apex of the head shield. The doublure is narrow at the sides; along the posterior margin it is 2 mm wide in medium sized specimens.
Abdomen. The abdomen is broad and depressed in the anterior portion and narrow and tubular in the posterior portion, the two parts contrasting in a most striking manner. The dorsal side of the anterior preabdomen appears to have been entirely flat, but the middle third of the posterior part projects above the flat or slightly concave pleural portions
