Ig2 NEW YORK STATE MUSEUM 
Horizon and locality. Frankfort shale (Schenectady beds) near Rotter- 
dam 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 com- 
parable 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 
Plate 20, figures 2-10 
Eurypterus microphthalmus Hall. Palaeontology of New York. 1859. 
3: 407*, pl. 80A, fig. 7 
Kurypterus 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 preabdo- 
men. 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. Itsoutline is evenly rounded. Itisslightly promi- | 
nent, reaching its apex between the lateral eyes, whence it rapidly declines 
forward and gradually backward. 
