primitive condition as natatory organs and their functional adaptation to walking organs. The coxae of the swimming legs are distinctly seen in the type specimen. They are relatively small, considerably less than one half the length of the carapace, long at their inner margin and subrhomboidal in general outline, the anterior and posterior margins being rather oblique and long. The fourth, fifth and sixth segments are longer than in the later species of Eurypterus and distinctly tubular, while the seventh and eighth are not nearly of the relative size and width in E. remipes or E. fischeri. Both are about equal in length, not longer than the preceding ones. The seventh segment is as wide as long and the eighth subcircular. The terminal spine is more than half as long as the preceding segment, slightly curved. The metastoma is small, measuring little more than one third the length of the carapace, oval in form; the anterior portion slightly narrower than the posterior one.
The genital appendages have been clearly seen in only one specimen, a female [pl. 26, fig. 2]. They are here so long that they reach to the posterior margin of the third sternite. The paired basal plates are visible only in faint outline. They were apparently of the usual shape. The first median lobe distinctly spreads in posterior direction and its paired extremities are produced into relatively long laterally curved alae that extend to the posterior margin of the second sternite. The second median lobe is but little shorter than the first and of less, though uniform, width. The terminal paired appendages are long (as long as the second median lobe) and slender, slightly curved outward.
Ornamentation. The type specimen shows on the last postabdominal segments where patches of the surface are preserved, very small, evenly distributed, sharply angular or pointed scales.
Measurements. The type specimen is 136 mm long. Its carapace measures 28 mm in length and 34.7 mm in width; the preabdomen is 32.3 mm long and 39.4 mm wide; the postabdomen 42.2 mm long, 31 mm wide at its beginning and 12.5 mm at its posterior end. The telson is 30.4 mm. The metastoma is 9.5 mm long, the swimming legs are
