Length of last postabdominal segment, 16.5 mm
Width, 21.5 mm
Length of telson, 33 mm
Width, 23 mm
Total length of original specimen (not distended as in fossil state), 184 mm
Largest carapace observed:
Length of carapace, 28.5 mm
Width of carapace, 40.5 mm
Length of tergite, 23 mm
Width, 73 mm
A very large tergite [text figure 71] collected at Litchfield and possibly belonging to this species, has a length of 10 cm and a width of about 37 cm.
The largest telson observed measures:
Length, 60.5 mm
Width, 49 mm
This telson, which undoubtedly belongs to P. macrophthalmus, indicates that the species attained at least twice the size of the complete individual represented on plate 69, figure 2 or a length of a foot and a half. If the large tergite from Litchfield belonged to this species, the animal reached a size of about 1.65 m or 5 feet, 5 inches.
Remarks. The species P. macrophthalmus was founded upon the carapace of a young individual from the waterlime at Litchfield, Herkimer co., N. Y. At the same time a specimen lacking the carapace, and showing only four segments of the abdomen and the ventral side of the cephalothorax was made the type of another species, P. osborni. This specimen came from the same horizon, and a locality a few miles distant from Litchfield, viz, Waterville, Oneida co. A separate metastoma [op. cit. pl. 80A, p. 16] of the same shape as that shown in the type of P. osborni was also referred to the latter species.
While it was the correct procedure to erect different species for the carapace and the abdomen as long as the parts had not been found con-
