Horizon and locality. Frankfort shale (Schenectady beds) near Rotterdam Junction, Schenectady co., N. Y.
Remarks. This species is remarkable in several regards; mainly in the extraordinary size of the eyes, which in relative proportion are comparable to the eyes in larval stages. Their submarginal position and the round shape of the carapace give the form a distinct pterygotoid aspect, but the eye node and the visual surface are those of an Eurypterus. This species with its larval eyes and other features indicating the traits of a synthetic type promises, when better known, interesting data relating to the phylogeny of the eurypterids.
Eurypterus microphthalmus Hall
Eurypterus microphthalmus Hall. Palaeontology of New York. 1859. 3:407*, pl. 80A, fig. 7
Eurypterus eriensis Whitfield. N. Y. Acad. Sci. Ann. 1882. 2:196
Eurypterus eriensis Whitfield. Geol. Sur. of Ohio. 1893. 7:416, pl. 1, fig. 31, 32
Description. The entire animal is small, but robustly built. The cephalothorax is relatively large, its length equal to that of the preabdomen. The body is sharply divided into the broad, short preabdomen and the narrow, cylindrical postabdomen. While the carapace was slightly elevated, the segments of the preabdomen were strongly arched, increasing in hight posteriorly and the last four segments were circular in section. The carapace and the preabdomen together form a compact oval, at the narrow end of which the taillike postabdomen is inserted, the whole body much resembling a tadpole in its last stage. The integument of this form seems to have been relatively strong.
The carapace is semielliptic, approaching the semicircular form and outline; its length to width approximately as 2 : 3 and in older individuals approximately as 3 : 4. Its outline is evenly rounded. It is slightly prominent, reaching its apex between the lateral eyes, whence it rapidly declines forward and gradually backward.
