tinctions on the determinations made by Holm in Eurypterus fischeri, this appendage in the female consists of a narrow, convex, scalelike, sagittate-based sheath, which appears to be formed by the fusion of two nearly equal portions, the anterior overlapping, and projecting posteriorly to cover partially a slightly shorter, simple, lance-linear appendage in a cleft of the following sternite. In the male the appendage is confined to the first sternite, the second being entire. It is proportionally shorter and broader, convex and lanceolate with the posterior free end slightly produced. Postabdomen composed of six ring segments. The first is readily distinguished from the segments of the preabdomen by postlateral prolongations. It appears to be formed by the fusion at their appressed ends, of a sternal and a tergal portion, the latter of which is the longer. The following segments are simple, bandlike rings. Telson long, lanceolate, with dorsal carination. Epistoma convex, peltiform, dividing in molting or under stress of compression, through the middle, joined at the sides to a narrow doublure. Preoral appendages attached at the posterior end of the epistoma; short, stout, composed of three joints, the two distal a little shorter than the basal, and forming a pair of edentulous, bevel-edged pincers, which normally are folded back so that their tips converge close to the anterior end of the mouth. Endognathites increasing in length from the first backward, moderately robust, spiniform, composed of seven joints, of which the third to the sixth inclusive bear a pair of spines. Swimming arms narrow, lanceolate paddles, composed of eight joints and a rudimentary ninth inserted in a notch on the inner side of the eighth or palette. The proximal joint, or gnathobase, has the form of an upright retort. The seventh bears on the inner half of the distal end a subtriangular lobe demarked by a suture. Metastoma elongate, cordate.
Type, H. socialis Sarle.
In the elaborate comparison with other genera which Mr Sarle adds to the generic diagnosis, the characters suggesting Pterygotus, as well as the resemblances to Eurypterus and Slimonia, are fully discussed. Since the date of his study the rocks of New York have afforded representations of this interesting genus in the Shawangunk grit and the Frankfort shale. These new forms suggest a somewhat different conception of the relationships of Hughmilleria, which is most conveniently set forth by annotating Sarle's discussion of the relationships of the genus.
