about 52 mm long each. Judging from the size of the genital appendages (in specimen 12909 University of Chicago) all specimens before us are of mature age and the species probably did not reach a much larger size than that exhibited by the largest specimen before us. This attained a length of 125 mm to the base of the telson (which is but partly preserved), to which may be added at least 34 mm for the telson, giving a total length of 159+ mm, to which corresponds a greatest width of 50.5 mm, a figure clearly exaggerated by the strong flattening of the specimen. The carapace measures 33.7 × 40 mm. The eyes were about 7.6 mm long and the amount of their length distant from the margin. The limbs appear very small in this specimen; the swimming legs extending but 44 mm beyond the lateral margin of the carapace.
Horizon and locality. Noblesville waterlime at Kokomo, Indiana.
Remarks. The material before us consists of four specimens, three from the museum of Chicago University, among these the type, and one from the collections of the State Museum. The type specimen is exceptionally preserved for Kokomo eurypterids. It exhibits all details of structure but the original figure does not do it justice as the specimen had not then been worked out nor the extremities of the limbs, among them the curious spines of the paddles, exposed. For these reasons this specimen has been refigured [pl. 25, fig. 1] and a drawing added of one of the other specimens [pl. 25, fig. 2] which shows the faint outlines of the eyes, and is remarkable for its size and exhibits well the terminal spines of the paddles. The third specimen is entirely unique in its preservation [pl. 26, fig. 2]. As shown in the reproduction, the gill plates are preserved as thick, black, roughly surfaced blotches, while the whole specimen appears as hardly more than a color stain. We have more fully referred to this specimen in the general remarks on Eurypterus. The doublures of the segments also come out with remarkable distinctness as dark bands and the female opercular appendage is distinctly set off from the darker background. The sutures of the basal plates of this appendage are barely discernible.
