1 10 MR. F. E. BKDDARD 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 tubercnlate on the proximal joints ; 

 the nropoda 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 

 milhm., the antennse measure 60 milhm. The males differ slightly 

 from the females, tlie latter being wider in the thoracic region and more 

 spiny. The anterior margin of the head is excavated ; 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 j)osterior 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 (he 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 tubercnlate, 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 uropnda are tuberculate. 



Station 146; 137.5 fathoms. 



