Page:The Eurypterida of New York Volume 1.pdf/204

 three, each joint from the third to the penultimate is provided with two long, curved, striated spines. The terminal joints are comparatively long and clawlike. The coxal joints are large. The first three are short and broad, the length being a little less than two thirds the breadth. They have narrow, curved, postlateral prolongations equal in length to the second joint. The lower, inner angles are rounded and crenulated. The dentate faces at the inner, upper angles are on slight prolongations, which grow longer with each succeeding coxa. All three begin with two or three isolated, anteriorly directed, lobelike teeth, followed by slender conic ones, which become finer toward the posterior end. The fourth coxal joint is comparatively long. The inner lower angle is gently rounded away, and the neck supporting the narrow dentate face, long. The teeth appear to be comparatively few and coarse. The epicoxite of the third left coxa is shown on plate 16, figure 1.

The swimming arms are stout and moderately long, extending back nearly to the fifth tergite, and consist of nine joints. The gnathobases are subquadrate and large, and are provided with seven or eight short, bevel-edged denticles, the two anterior being large and prominent. The length of the gnathobase was 33 mm, its breadth 30 mm, the length of the dentate face 8 mm. The middle joints have the anterior and posterior angles sharp, in the fifth the anterior forming a blunt, striated spine, much like those at the sides of the postabdomen. The seventh and eighth joints are broadly expanded, and their margins, particularly in the latter, are marked by sparse, shallow serrations. Inserted on the inner side and near the end of the eighth joint, is a small, oval, rudimentary ninth joint.

The metastoma is elongate ovate, widest in the middle, with ends truncated. The anterior or narrower end is notched and minutely dentate.

The genital appendages of this species, so far as they are preserved in the material of the collection, are, with the exception of the part carried by the second sternite in the female, essentially like those of  Eichw., as described by Holm. That of the female is the more complex and is carried partly by the operculum and partly by the second sternite. The part carried by the operculum follows two subtriangular areas formed by a pair of sutures extending posteriorly from either side the median lobe to meet the cleft, and extends considerably beyond the posterior edge of the plate. It consists of a short sagittate base and a slender portion divided transversely into two imbricating sections, each terminating in a short bifid expansion. In  there is a third part consisting of two, short, flat, diverging crura. As this appears to be a general feature in Eurypterus, it is probable that it exists in this species also. The part of the appendage carried by the second sternite is covered by that of the operculum. It lies in the median cleft which extends through the posterior two thirds of the sternite, the anterior third