Description. Body medium-sized to large. Carapace semicircular, nearly twice as wide at base as long (length : width as 6 : 11), probably originally quite high (as indicated by concentric wrinkles); lateral and frontal margins forming a continuous circular curve, when the carapace is flattened; the thickened edge scalloped; posterior margin straight and transverse, genal angles nearly rectangular; compound eyes relatively small (one seventh the length of carapace), consisting of a bean-shaped, very prominent ocular node and narrow reniform visual surface, situated halfway between the frontal and basal margins, far apart (three fourths as far from lateral margin as apart); the ocellar node prominent, in exact middle of carapace.
First tergite one fifth as long as the carapace, nine times as wide as long. Postlateral angles truncate. Postabdomen at its anterior end about three fourths as wide as long and tapering to about one third of its anterior width. The segments possess distinct epimera which become increasingly winglike posteriorly, on the last segments possessing sigmoidal margins.
Ornamentation. The ornamentation of the carapace and postabdominal segments has been described above. From an exfoliated portion of one specimen [pl. 23, fig. 1] it is seen that the test of the marginal shield of the cephalothorax was furnished with wartlike, round pustules.
Measurements. Carapace of type, 67 × 120 mm (as 6 : 10.7); that of Pohlman's type of E. giganteus 50 × 93 mm (as 6 : 11). Eyes in type 41 mm apart and 30 mm from lateral margin; in other specimen 7 mm long, 31 mm apart and 24 mm from margins. First tergite of this specimen 9.5 mm long. Postabdomen about 150 mm wide at anterior end, 210 mm long and about 50 mm at posterior end.
Horizon and locality. Bertie waterlime at Buffalo.
Remarks. A third carapace (with attached first tergite) of like dimensions with the type of the species is in the Buffalo Museum. It is noteworthy for the distinctness of the ornamentation of the first tergite, consisting of a narrow anterior zone of very closely arranged tubercles and the characteristic disklike scales which here are larger, more numerous, and
