rounded and in many the disk is distinctly heart-shaped. About the center are two darker spots which represent a pair of pitlike depressions. The scales are largest and most crowded on the anterior half of the segment. The overlapped anterior fifth of the segment is sharply set off from the remainder by a line of oval disklike scars and the overlapped part itself is densely crowded with smaller scales which in front consist of crescents and behind change gradually into the disks, thereby evincing the morphologic and functional identity of these peculiar disklike scales with the crescentic scale of other eurypterids.
A brief study of the ornamentation of Pohlman's type of E. giganteus ( = E. pustulosus Hall) figured on the same plate as his Pterygotus globicaudatus, shows it to be of quite the same character and relative dimensions as the latter, the fact being taken into account that the sculpture pustules of the eurypterids are always of smaller size and at the same time more prominent on the carapace than on the body. The enlargements of the ornamentation of the type of E. giganteus [pl. 24, fig. 2, 3] show that the carapace was covered with large wartlike pustules in front of the eyes, which are flat on top or slightly sunken in. They are now filled with rock and were hence originally hollow and probably rounded on top. Between them are found many smaller ones, scalelike, with thicker test, which exhibit the disk shape of those of P. globicaudatus, as seen on the anterior portions of the segments [pl. 24, fig. 4]. Like scales are observed on the first tergite of the type of E. giganteus and since the sculpturing as a rule increases in coarseness from the first tergites posteriorly, there is no doubt that this ornamentation fully corresponds to that seen on the postabdomen of P. globicaudatus.
It is hence, manifest that P. globicaudatus and E. giganteus are of the same species and as E. giganteus is identical with E. pustulosus the original P. globicaudatus represents the postabdomen of E. pustulosus. The species characters are then the following:
