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Show 1900.] FROM THE FALKLAND ISLANDS. 557 on the left than on the right mandible; molar cylindrical, with spines above, as well as the usual spine-row; spines on the second and third joints of the palp pectinate. First maxillae.-Inner plate narrow, with four plumose setae at the apex, outer plate with a lobe below the middle, and on the apex nine stout, and three slender, somewhat denticulate spines. Maxillipeds.-Second joint wide at the base, then narrow, its plate narrow at the base, then wide, the apical margin broad, carrying numerous plumose spines; third joint short; fourth narrow at base, the lobed distal end wide; fifth much shorter but about as wide distally ; sixth longer than fifth or seventh, much narrower than fifth, with a short lobe at its widened distal end ; seventh narrow, not unguiform. The fifth and sixth joints are not without armature of the inner margin, but it is far less conspicuous than the long setae which those joints display in Sphceroma serratum. Here, as in Sphceroma curtum, the fifth joint is decidedly smaller than the fourth, but in Sphceroma rugicauda the fifth joint is larger than the fourth, as in Sphceroma serratum. Limbs of the peraeon.-In these there is a gradual increase of length, so that the seventh pair is considerably longer than the first. In all, the third joint is elongate, without the long setae displayed in Sphceroma serratum; the fourth, fifth, and sixth joints are thickly furred along tbe forward margin, the fourth and fifth having a group of small spines on the backward apex ; the sixth has at the apex, on the inner side, as in various other Sphaeromidae, and in Isopoda of other families, a rounded plate overlapping the base of the finger; the finger is of the kind called bidentate, one tooth being the short, curved, horny-looking nail, the other a small spine near the base of the nail. The appendages of the male on the seventh peraeon-segment are rather long, about four times as long as broad. Pleopods.-The first pair are smaller than the second. Tbe male appendage of the second is considerably longer than the rami, apart from their long fringes of plumose setae, and ends almost acutely, not being roundly expanded at the apex as in Sphceroma rugicauda. The covering ramus in the last three pairs has a transverse suture near the end; the under ramus of the fourth and fifth pairs is much plicated. Uropods.-The lower outer branch is a little broader and apically a little more broadly rounded than the inner, which is sometimes spoken of as a prolongation of the peduncle, there being, in fact, no articulation between them. One of Mr. Vallentin's specimens is distinguished from the rest as follows :-It has the sides of tbe peraeon-segments abruptly down-bent, so as to form a sharp angle with the middle of the back ; on the fourth pleon-segment are a pair of little median humps, such as are barely indicated in tbe other specimens ; the pleon-shield has the median fine occupied by a longitudinal groove between two elevations, and then by a carina of which the first part is divided between two tubercles, the remainder running to P R O C ZOOL. Soc-1900, No. XXXVII. 37 |
