^8 CRUSTACEA MALACOSTRACA III. 



distal joints of the peduncle with flagellum lost in my specimens). — Maxillipeds (fig. 6 d) in the main 

 as in I. profundus, excepting that the epipod is considerably smaller, having more than half of the 

 outer margin concave. 



Each of the four anterior thoracic segments (fig. 6 a) anteriorly at the sides produced into a 

 pair of somewhat long, subacute processes directed forwards, considerably outwards and distinctly up- 

 wards; the anterior margin of each process is about, or scarcely, half as long as the front margin of 

 the corresponding segment between the origin of the processes (fig. 6 b). Fifth and sixth segments 

 each posteriorly produced into a pair of similar processes directed backwards and somewhat outwards, 

 but not upwards; the posterior pair of these processes are conspicuously longer than any of the other 

 pairs. Fourth segment much produced backwards, being somewhat longer than second and third seg- 

 ments combined; fifth segment distinctly less than half as long again as the fourth, moderately slender, 

 slightly more than four times as long as its breadth near the front end. 



First pair of thoracic legs (fig. 6 e) more slender than in I. profundus'^ fifth joint more than 

 twice as long as deep, with a protruding angle on the lower side somewhat from the base; this angle 

 bears a long spine, and a still longer spine is somewhat more proximal, while the major, distal part 

 of the lower margin is distinctly concave without spines; sixth joint is somewhat shorter than the 

 fifth, more than three times as long as deep, without spines, and twice as long as seventh joint with 

 claw. The other legs nearly all lost excepting the proximal joints; second joint of fourth pair reaches 

 scarcely to the end of its segment, and is rather far from reaching the end of second joint of fifth leg. 



Abdomen with the first segment very short but very distinct (fig. 6 a). Second segment scarcely 

 one-third as long again as broad, scarcely narrower at the anterior than at the posterior margin; the 

 lateral margins are considerably convex excepting a little from the end, where they bend backwards 

 and a little outwards (fig-. 6 f); the posterior margin is somewhat convex, with the uropods at its ends. 

 The ventral excavation occupies nearly the whole surface excepting a moderately large posterior por- 

 tion, and its hind margin is very convex. — The median lamella of the operculum is very large, 

 distinctly narrowed near the base and then gradually a little expanded, with the lateral margins sub- 

 parallel from before the middle to near the broadly rounded end of each pleopod; the lateral plates 

 of the operculum unusually narrow. — The uropods scarcely half as long as the breadth of abdomen, 

 two-jointed, and first joint not half as long as the second; no exopod. 



Length of the male 4-8 mm. 



Remarks. This fine species is abundantly distinguished from all other species of the group 

 by the number and development of thoracic spines. In the outline of the abdomen and especially in 

 the shape and relative size of the opercular plates it differs much from the two other species of the 

 genus. But at least at the present state of our knowledge these differences are far from sufficient for 

 establishing a new genus on I. armatus. 



Occurrence. Taken by the "Ingolf" at a single station. 



Davis Strait: Stat. 36: Lat. 6i°5o' N., Long. 56°2i' W., 1435 fath., temp. 1-5°; 2 males. 



