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; auteriorly 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 antennze and of all the thoracic limbs are beset 
with tubercles. 
Station 169; 700 fathoms. 
2. ARCTURUS ANNA, 0. sp. 
This single specimen of this large species measures 37 millim. ; 
the antenne 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 ina 
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. 
