The specimen figure 3 has suffered strong compression in anteroposterior direction and is therefore not competent to indicate the form of the carapace in this stage, but it corroborates the evidence from the other as to the relatively increased size of the compound eyes and the distinctness and position of the ocelli.
The carapace has lost its position as the broadest part of the body, the preabdomen having been completed and become the widest portion. In other growth-stages of eurypterids obtained at Otisville, the postabdomen is completed before the preabdomen, and it is hence to be inferred that in the specimen figure 3 the number of segments is complete. This is also suggested by the presence of a narrower first preabdominal tergite such as is found in the mature stage.
The compound eyes are relatively larger than in the nepionic stage, occupying fully one half the sides of the carapace, but less prominent. The compound eyes of the first specimen are especially notable for the distinctness with which a thickened ring is seen to surround the inner side of the eye. The same is already visible on the second nepionic specimen figure 2 and partially noticeable on the type. It probably surrounded the whole eye and its function was apparently to support the prominent cornea, corresponding in that to the orbital ridge in Stylonurus excelsior.
| Measurements. | |
| Type, carapace, length, 12.3 mm; width, 15.5 mm | |
| Length of first tergite, 1.5 mm | |
| Width of largest tergite observed [pl. 82, fig. 8], 25.5 mm | |
| Length of same, 9.9 mm | |
| Largest telson observed [pl. 82, fig. 11], length (incomplete), 35 mm; width (restored), 60.2 mm | |
| Smaller telson, width, 7.4 mm; length, 7.7 mm | |
| Smallest specimen, length (incomplete), 1.6 mm; width, .8 mm | |
Horizon and locality. Rare in the Shawangunk grit at Otisville, N. Y.
