pl. 3, fig. 3] and which is now in the collection of Columbia University, proves to be a carapace of Dolichopterus siluriceps [pl. 26, fig. 3], in which the eyes are normally intramarginal. We have however specimens of Eusarcus scorpionis which leave no doubt of the marginal position of the eyes in that species, and thus afford an important differential of the genus. In none of the British species with typically Eusarcuslike outlines (viz, Eurypterus scorpioides and E. punctatus) was the position of the eyes known to Woodward, and one species, of which only the triangular carapace and subcircular abdomen have been found, was referred by him to Pterygotus (P. raniceps) on the strength of its marginal eyes.
Grote and Pitt based their new genus on mere differences in outline and though Woodward did not regard these as generic characters, and Miller [N. A. Geol. & Pal. 1889, p. 548], obviously for like reasons, refused to recognize the genus, while Zittel cites it as doubtful, it is entirely evident from our present knowledge that the group, typically represented by Eusarcus scorpionis, is generically distinct from all its allies.
On this continent there is another locality, Kokomo, Indiana, which has afforded representatives of Eusarcus sometimes in gigantic examples. The first specimens were described by Claypole as Eurysoma newlini [1890, p. 259]. The term Eurysoma was soon after withdrawn by its author as preoccupied and was replaced by Carcinosoma. In 1894 another species (C. ingens) from the same locality was added and Eusarcus indicated as the nearest ally of the new genus, with the following qualification: "But the description of that genus [Eusarcus] mentions that the cephalothoracic portion is considerably narrower than in allied forms and that the terminal segment shows a widening and no trace of spiniform process. There are also several other minor points of difference." None of the differences here suggested by Claypole really exist, for our working material, which probably comprises nearly all Kokomo specimens ever collected, shows this carapace to have quite the same subtriangular form as in the Buffalo specimens, while both possess an ensiform
