OCR Text |
Show 1886.] DURING THE VOYAGE OF H.M.S. 'CHALLENGER.' 107 individual measures about 9 millim. The first four thoracic segments are subequal in length ; each is ridged posteriorly, the ridge widening out laterally to occupy the whole of the segment, it is covered with fine granulations ; in the fourth segment the ridge is higher than in the preceding segments ; anteriorly between the ridge and the anterior margin of the segment is a shorter ridge, likewise covered with numerous minute tubercles ; on the first thoracic segment is a third ridge ; of the three posterior segments the first is the longest; on each is a posterior ridge-like elevation beset with numerous tubercles. The abdominal shield is oval, tapering towards its extremity, which is slightly upturned; like the thorax, it is tuberculate. The proximal joints of the antennae and of all the thoracic limbs are beset with tubercles. Station 169 ; 700 fathoms. 2. ARCTURUS ANNA, n. sp. This single specimen of this large species measures 37 millim. ; the antennas are nearly twice the length of the body. The head is excavated in front ; the antero-lateral margin of the head is notched ventrally. The first four segments of the thorax are subequal; each is traversed by a ridge, which dorsally is narrow and only occupies the posterior portion of the segment, laterally it is widened out and occupies the whole of the segment; in front is another shorter ridge, which does not reach the lateral region of the segment; at the extreme lateral margin is a stout spine, inclined nearly at right angles to the longitudinal axis, which overlies the epimeron ; behind are one or two shorter spines along the postero-lateral border of the tergum. The epimera, which are short, are likewise furnished with one or two short spines ; these are only conspicuously developed upon the last two of the segments, especially upon the last, where one of the spines equals in length the tergal spine which it directly underlies. Of the three posterior segments the first is decidedly the largest; they are ridged like the anterior segments, the ridge widening out laterally ; each segment has a short lateral spine corresponding to those on the anterior segments ; the epimera are also furnished with a stout spine, that of the fifth segment with an additional spine directed forwards. There are two completely free abdominal segments, the third being to a large extent fused with the abdominal shield ; on the ventral side of the first abdominal segment is a short spine on either side anteriorly and another pair of longer spines posteriorly ; this segment as well as the next has a short lateral spine ; the third abdominal segment has on either side a long curved spine at the postero-lateral margin. The abdominal shield has a central convexity occupying nearly the whole of its extent and bordered by a flattened rim, which is serrated, and terminates posteriorly in a pair of pointed processes projecting behind the central area, which terminates posteriorly in a short pointed spine. The thoracic limbs of the second, third, and fourth pairs have one or two longish spines on the three proximal joints. Station 320; 600 fathoms. |