Page:The Eurypterida of New York Volume 1.pdf/254

 existence, they could be of no more than varietal importance. We here refer all specimens of Eusarcus from Kokomo to one species which has the following characters.

Description. General form that of a rather short, posteriorly broad oval body (carapace and preabdomen) with abruptly attached tubular tail (postabdomen) of equal length with the body, and a rather short, stout tail spine.

Cephalothorax broader than long (proportion of length to width as 7 : 8 in the youngest specimen), the difference decreasing with increasing age, in the largest example being reduced to but one fourth of its earlier size; outline a regular triangle with truncated angles, the lateral margins moderately convex, the posterior margin gently concave in the middle, almost straight. Posterior truncating line or postlateral angles very gently convex; frontal margin probably slightly emarginate between the eyes. The lateral eyes have been seen only in the largest specimen; they are located at the antelateral angles, are of bean-shaped outline and about one fifth the length of the lateral margin. Their structure has not been observed; nor have the ocelli been seen in any of the specimens.

Abdomen. Preabdomen relatively shorter than in any of the other species; a little longer than the carapace and nearly twice as wide; broadens in continuation of the lateral margins of the carapace to the fourth tergite, whence it contracts rapidly to the powerful postabdomen which is twice as long as the preabdomen and two fifths as broad.

The outlines of the separate tergites and sternites have not been distinguished with clearness and no separate plates observed; hence no detailed description of their form and relative dimensions can be given, but enough has been seen to prove that they do not differ materially from the corresponding parts of the better known, although it is