preabdomen, since the latter is here only as long as the carapace, while in the resulting adult it is longer by one fourth.
The postabdomen in the young exhibits its usual proportions.
The ornamentation of the dorsal side shows a difference between the neanic and ephebic forms in the recognizable number of longitudinal series of scales, the former possessing but four on the anterior preabdominal and two on the following segments as against six and two in the ephebic stage.
Measurements. A well preserved and normal specimen, plate 5, figure 5, gives the following figures: length and width of carapace, 18.7 mm and 24.5 mm; length and width of preabdomen, 27.3 mm and 27 mm; length of postabdomen, 40.4 mm; its anterior and posterior widths, 20 and 7 mm. The telson measures 28 mm and is 5 mm wide at its beginning. The lateral eyes of this specimen are 5 mm long and 5.5 mm from the frontal margin. The first tergite is 3.6 mm long and 25.5 mm wide, the third about 6 mm long and 27.4 mm wide. The first postabdominal segment is 6 mm long and 19 mm wide in the middle, the last measures 10.5 mm by 8.5 mm.
The largest carapace observed is 50 mm in length and 67 mm in width; the one figured on plate 6, figure 3 is 45 × 60 mm.
Horizon and localities. DeKay's type of this species came from Waterville, town of Westmoreland, Oneida co., N. Y. Hall's numerous originals were partly from the same locality and in still greater number from Jerusalem or Wheelock's hill, Litchfield, Herkimer co., N. Y. which, with its neighborhood, has to this day furnished the principal supply of this species. In late years it also has been obtained in great numbers a few miles northeast (near Cedarville) and west (Paris Hill) of Jerusalem hill. It occurs near Oriskany; at Cayuga junction, Cayuga co. and possibly at Buffalo. In all these localities it has been found in the uppermost part of the Bertie waterlime, near the overlying Cobleskill limestone. But we have also from Seneca Falls, Seneca co., typical specimens from the Rondout waterlime above the Cobleskill limestone.
