in form, its proximal margin furnished with a strong process that fits into the corresponding notch of segment five, forming a strong articulation, and its distal margin is produced bluntly to articulate with the seventh segment. The latter is the largest one in the swimming leg after the coxa. Its longest edge equals in length the preceding five segments. It is oval in form, as in other species, flat and expands toward the distal end. Its proximal margin is bilobed for articulation with the sixth segment and its distal margin is bluntly indented in the middle for the articulation with the next segment. The outer lateral margin is slightly convex, the inner nearly straight. Both are thickened to strengthen the bladelike expansion. The distal portions of the lateral margin are distinctly serrate. The rather large triangular process of the inner side of the distal margin is, as in the other eurypterids, set off from the rest of the segment by a straight suture. The eighth (paddle) is a little shorter than the seventh, but markedly more slender; it is long, ovate, with lanceolate distal part. Its inner lateral margin is coarsely and its outer margin finely, serrate. The single perfect paddle of our material carries at its distal end a distinct disklike "terminal palette."
The metastoma is elongate cordate; its greatest width about one third the length from the anterior margin. The width equals three fifths of the length. The posterior extremity is well rounded in some specimens and apparently truncated in others. The "Umschlag" or doublure of the inner face, is distinctly seen in one of the specimens [pl. 77, fig. 1] and the wrinkling caused by the compression of the membrane is visible in the figure. In some specimens [pl. 78, fig. 4] a deep median furrow or cleft extended about one third of its length. The inner face was smooth, the outer sculptured as described below.
The epistoma has not been observed. The endostoma was, however, observed lying under a metastoma and accidentally turned backward [pl. 78, fig. 4]. It closely resembles in form the endostoma of Eurypterus fischeri. It is a thin suboval shield with deeply emarginate anterior margin. Its lateral and posterior boundaries are ill denned, as it there
