REPOET ON THE ISOPODA. 99 



longer than the first and fourth. Each of the four segments is ridged posteriorly, the 

 ridge being very narrow dorsally and widening out laterally as in other species; at the 

 junction of the tergum with the epimeron is a short blunt lateral tubercle, which over- 

 hangs and completely conceals the latter when the animal is viewed dorsally ; the 

 epimera, which are extremely short, are produced into a similar tubercle which exactly 

 underlies that of the tergum ; on the first segment the tubercle is prolonged into a 

 spine. 



The three posterior thoracic segments are shorter than any of the four anterior ones ; 

 the first is the longest of the three ; on its inferior surface is a transverse ridge which 

 reaches nearly right across the segment and bounds it anteriorly ; each of the segments 

 has a posterior ridge ; laterally there is a large rounded convexity separated by a shallow 

 furrow from the ridge and from the epimeron ; the latter is smooth. 



The antennules reach about half way along the third joint of the antennae. 



The two basal joints of the antennse are very short ; the third is twice the length of 

 the first two ; the fourth is half again as long as the third ; the fifth is longer still and 

 the flagellum half as long again. 



The anterior thoracic appendages (fig. 7) are furnished with one or two short spines 

 upon the proximal joints, the posterior thoracic appendages (fig. 8) have also a few 

 tubercles on the basal joint. 



At Station 184, off Cape York, two specimens of an Arcturus were dredged at a 

 depth of 1400 fathoms, which appear to belong to the same species, though it is rather 

 difficult to speak with certainty owing to the imperfect condition of the specimen from 

 Station 281, and the fact that the only perfect specimen from Station 184 was a female, 

 while the example of Arcturus dbyssicola, described above, is in all probability a male, 

 as there were no traces of ovigerous lamellae. This being the case, it will be better to 

 describe the characters of the specimens without regarding them, for the present at least, 

 as belonging to another species. 



The anterior thoracic segments are rather shorter in proportion, but otherwise present 

 pretty much the same characters. 



The abdominal segments are convex dorsally ; the first has a pair of short tubercles 

 ventrally on either side of the median line ; the sides of the segments are rather more 

 roughened than the thoracic segments. 



The caudal shield is keeled, and terminates in a blunt spine ; it is covered with a few 

 low scattered tubercles. 



Station 281, October 6, 1875, near the Low Archipelago ; lat. 22° 21' S., long. 

 150° 17' W.; depth, 2385 fathoms; bottom temperature; 34° - 9 F. ; bottom, red clay. 



Station 184, August 29, 1874, between Australia and New Guinea; lat. 12° 8' S., 

 long. 145° 10' E.; depth, 1400 fathoms; bottom temperature, 36° "0 F.; bottom, Globi- 

 gerina ooze. 



