in a still more striking manner in length, for the last segment is nearly four times as long as wide; the postabdominal segments thus change from short, wide rings to relatively long, narrow tubes, the last three being the most markedly subconical. The posterior doublures, about 4 mm wide, are well seen on plate 55. There are keels parallel and near to the lateral margins of the postabdominal segments. The telson is enormously developed. It not only occupies nearly one third of the length of the whole body, but is also very strong and thick. In shape it is clavate, contracted at about one fourth of its length and expanding again, and reaches its greatest width at three fourths of its length. Its extremity is blunt.
Appendages. Of the postoral appendages of the cephalothorax, the third to fifth pairs of limbs have been observed in position and one of the preceding limbs has been seen detached [pl. 55]. The latter is of strikingly plump form, its greatest width being nearly one third of its length. Its segments are narrow rings, seven in number, increasing in width to the third and then gradually decreasing to the long, curved terminal claw. The last five segments bear each a pair of short, blunt spines. These, like the terminal spine, are longitudinally striated. This limb contrasts so much in shape with the third limb that we should be inclined to consider it, in view of the regular series which the third to fifth limbs form, as the first postoral appendage. But as Laurie has regarded a similar short, stout appendage as the second leg in Stylonurus macrophthalmus [1899, pl. 1, fig. 4] and as the first limb of Stylonurus and Drepanopterus are practically unknown, we prefer to leave the question of the number of this leg open. The third limb is much longer, projecting with four and one half segments as much beyond the margin of the carapace as the base of the carapace is long. It is, however, not slender, its fourth joint being still two thirds as wide as long. The segments are tubular; each is narrower than the preceding, but widens again a little in the distal portion. Those exposed beyond the margin of the carapace bore two spines each at the distal articulation. The limb ends, like the others, in a terminal claw. The fourth limb is built on the same lines as that just described. It pro-
