110 MR. F. E. BEDDARD ON ISOPODA COLLECTED [Feb. 2, 
widens out laterally ; the ridge is concave forwards, dorsally, and 
closely embraces a median oval convexity which lies in front of it ; 
the fourth thoracic segment has a row of short tubercles, arranged 
in a semicircle with the concavity directed forward, on the ventral 
surface. Of the three posterior thoracic segments the first is the 
largest, the second and third being smaller and subequal; each of 
the segments is traversed dorsally by a strong ridge, which is tuber- 
culate ; the first of these segments has a number of short tubercles 
scattered over the ventral surface, and the two succeeding segments 
are ridged in the same region. The segments of the abdomen are 
comparatively smooth, being only slightly roughened laterally. 
The abdominal shield is smooth with the exception of the lateral 
margins, which are serrate ; it terminates in a short median spine. 
The thoracic appendages are tuberculate on the proximal joints ; 
the uropoda bear a single median longitudinal row of tubercles. 
Station 174; 600 fathoms. 
7. ARCTURUS SPINOSUS, N. sp. 
This is the largest of the deep-sea species, measuring up to 48 
millim., the antenne measure 60 millim. The males differ slightly 
from the females, the latter being wider in the thoracic region and more 
spiny. The anterior margin of the head is exeavated ; between and 
a little in front of the eyes are a pair of long spines, behind these 
are a pair of shorter spines; in the female there is an additional 
pair of spines situated outside these latter. Of the first four 
thoracic segments, the fourth is slightly the longest in the male; in 
the female all four are subequal. On the first three thoracic seg- 
ments, the posterior ridge bears three pairs of long spines situated at 
equidistant intervals; the fourth thoracic segment has only two 
pairs, but the epimera have each a long spine, wanting in the anterior 
segments. In the female the first thoracic segment has four pairs of 
spines, the other segments being as in the male; between these 
principal spines there are, however (in the female), numerous smaller 
spines, and the margins of the epimera are furnished with short 
spines; each of these segments has in both sexes an anterior ridge 
covered in the male with blunt tubercles, in the female these tuber- 
cles are pointed. Of the three posterior thoracic segments the first 
is the longest ; the posterior ridge is tuberculate, the tubercles being 
more strongly marked in the female ; the epimera of these segments 
have a large lateral spine. The three first abdominal segments are 
distinct ; the last free segment has a long lateral spine on either 
side in the female. The abdominal shield terminates in a single 
median spine, and in two longer upwardly curved lateral spines. 
The surface of the abdominal shield is tuberculate in the male and 
covered with short spines in the female ; in this sex there are in addi- 
tion a pair of moderately long lateral spines, situated just in front of 
the posterior lateral spine. The thoracic appendages in the female 
have a few short spines; in the male only the three last pairs are 
thus provided ; the uropoda are tuberculate. 
Station 146; 1375 fathoms. 
