Page:The Eurypterida of New York Volume 1.pdf/217

 possessing a similar broad carapace and preabdomen and a still shorter postabdomen. The slender swimming legs of  serve at once to distinguish it from this Buffalo species. Its nearest relative is obviously the  of the same locality with which it has many characters in common, notably the broad plump form of the body, the broad doublure and the weak development of the swimming legs. Its principal distinguishing character from the latter is the greater width of the carapace, as a comparison of figure 7, plate 17, and figure 1 on plate 25 will readily show. In  the width surpasses the length by one fifth and in   by one third. It is possible that these differences are only those of sex, a point that at present can not be determined since the opercular appendages of  are not distinctly shown.

A younger specimen (no. 12906, University of Chicago collection) [ pl. 18, fig. 2] is interesting in showing a relatively broader carapace and preabdomen, a shorter body, and more abrupt contraction to the postabdomen, which is much more slender than the rest of the body. It thus displays distinctly immature features, corresponding well to those observed in other eurypterids.

Description. Carapace subtrapezoidal, width (22 mm) a little less than twice the length (13.5 mm). Posterior margin slightly arched forward in the middle third, lateral margins curved, flatly sigmoidal, slightlv converging forward; frontal margin not clearly seen, but apparently gently convex.

The compound eye is elongate elliptical in outline, very large, one third of the length of the carapace (4 mm in type specimen), situated near the antelateral angle; the visual surface is long and curves far inward at both ends. The ocelli seem to be situated behind the center of the carapace.