Besides the carapaces, on which the species is based, a half complete specimen [pl. 85, fig. 13] has been obtained. This exhibits a form of the preabdomen corresponding to that of H. socialis, the genotype, if the slight axial contraction of the specimen is taken into account. The swimming leg of the right side can be distinguished in its outline. It is relatively longer than that of H. socialis.
Besides the carapaces two detached chelicerae resemble in their strong development and long pointed pincers more those of Hughmilleria than of any other genus [pl. 85, fig. 17, 18] and also detached body rings [pl. 85, fig. 19] exhibit a type of ornamentation, consisting of transverse lines near the anterior margin, known to us only in H. shawangunk, the Otisville representative of the genus.
Hughmilleria shawangunk Clarke
Plates 64–66; 69, figure 1
Hughmilleria shawangunk Clarke. N. Y. State Mus. Bul. 107. 1907. p. 308, pl. 4, fig. 1–4; pl. 5, fig. 1–9
Description. Hughmilleria shawangunk attains but half the size of the genotype, or about 8 cm and is therefore one of the diminutive species of eurypterids. In outline of body and form of head it closely resembles H. socialis; it is slender and terete, but slightly wider in the middle of the preabdomen than at the base of the carapace, and lacks any marked contraction from preabdomen to postabdomen. With the anteriorly rounded, subtriangular carapace and marginal eyes, the dorsal aspect of the animal is singularly fishlike and suggestive of great agility.
Cephalothorax. The carapace is semielliptic in the mature form, wider than long by one sixth to one fifth, comprises one fifth the length of the body or more; as preserved it is subject to great variations in outline, mostly due to variously directed compression and wrinkling after entombment and to an originally thin test. The lateral margins of the carapace are slightly convex, the frontal part acutely rounded. The
