We are thus convinced that P. cobbi, although represented only by a free ramus, deserves recognition as a separate species. Its full characters will have to be established by future discoveries. For the present we base the description on the better preserved second specimen.
The main body of the ramus is nearly straight, its outer edge slightly convex, the inner slightly elevated in the middle in support of the largest tooth. It tapers uniformly, diminishing in width from the articulating extremity to the base of the terminal tooth by one half. It bears three series of teeth, one, consisting of the largest (four in this specimen) and culminating in the second tooth, and another only half as long, intercalated between the large teeth. A few teeth of a third order again half as long as those of the second order are noticeable near the basal part of the ramus.
The teeth possess a very slight forward curvature and stand at right angles on the jaw with the exception of those of the second order near the base, which correspond to the oblique direction of that part, and are directed forward. Fine longitudinal lines are noticeable on the teeth. The distal end of the ramus curves somewhat abruptly into a tooth, longer by one fourth than the culminating tooth of the middle part of the ramus and subparallel to it.
The length of the ramus is 13 cm (5⅛ inches). Its width at the base is 16.8 mm. The culminating tooth measures 19.4 mm.
If we assume that this ramus possessed the same proportional size to the length of the body as in other members of the genus, we derive an individual 6 feet, 7 inches long. Whatever the actual dimensions of this eurypterid may have been, the size and aspect of the jaw are convincing proof of its formidable character.
Pterygotus (Erettopterus) globiceps nov.
Plate 82, figures 1–12
Eurypterus maria (in part) Clarke. N. Y. State Mus. Bul. 107, pl. 2, fig. 3
The presence of a true Pterygotus in the Otisville fauna is shown by several carapaces, a few body segments, a swimming leg and several tel-
