CRUSTACEA MALACOSTRACA. III. 



57 



First thoracic segment of a somewhat quadrangular aspect, as the major part of the lateral 

 margins are subparallel; each anterolateral corner produced in a conspicuous, but somewhat small, 

 process projecting horizontally forwards. The other thoracic segments without processes. Fourth seg- 

 ment almost as long as second and third combined; fifth segment almost half as long again as the 

 fourth, and nearly four times as long as the breadth near its front end. 



First pair of thoracic legs (fig. 5 d) robust; fifth joint somewhat curved, much thickened with 

 a protruding, rounded part somewhat from the base, and this part set with some spines of very dif- 

 ferent length, while the lower margin between the top of the protuberance and the distal end is some- 

 what concave; sixth joint slightly shorter than the fifth, scarcely three times as long as deep, without 

 spines; seventh joint with claw somewhat strong, about half as long as sixth joint. The other pairs 

 lost excepting a few joints; second joint of fourth pair reaches slightly beyond the posterior end of 

 its segment, while the corresponding joint of fifth pair, when directed forwards, is rather far from 

 reaching the end of second joint of fourth pair. 



Abdomen (fig. 5 e) has its first segment very short but very distinct Second segment about 

 one-third as long again as broad, anteriorly considerably narrower than near the end; the lateral 

 margins are somewhat convex, scarcely concave near the postero-lateral angles, which are well defined 

 and sharp; the posterior margin with its major part considerably convex, and feebly concave towards 

 the angles mentioned. The ventral excavation for the reception of the pleopods (fig. 5 f) with its 

 posterior margin long, transverse and straight, leaving a considerable area between itself and the 

 posterior margin; the median lamella of the operculum small, tapering from somewhat from the base to 

 the narrow end, which does not reach the posterior margin of second pair of pleopods. (Uropods lost). 



Length of the specimen 4 mm. 



Remarks. I. profundus is allied to I. bispinosus G. O. Sars, but is considerably longer, and 

 differs besides in several particulars. The processes of first segment project nearly forwards, and 

 consequently slightly diverging, while in the male I. bispinosus they are longer and considerably diver- 

 gent (comp. Sars' Account PI. 52). Fifth thoracic segment less elongate than in the male I. bispinosus; 

 the prehensile organ of first legs is somewhat different in shape and in number, length and place of 

 spines; the last abdominal segment differs in having sharply pronounced postero-lateral angles, etc. 



Occurrence. Taken by the "Ingolf" at its deepest station. 



South of Davis Strait: Stat. 38: Lat. 59°i2' N., Long. 5i°05' W., 1870 fath., temp. 1-3°; 1 spec. 



35. Ischnomesus armatus n. sp. 

 (PI. IV, figs. 6 a— 6 f). 



Male. The body nearly seven times as long as the breadth of the first thoracic segment, 

 measured without taking its processes into account. — Antennulae (fig. 6 b) reaching slightly beyond 

 the posterior margin of second thoracic segment; second joint somewhat robust, slightly more than 

 half as long as the entire antennula, with two or three spines along the interior margin; third joint 

 thin and only one-fourth as long as second joint; first joint of the flagellum much shorter than the 

 second or the third. Third joint of the antennal peduncle not twice as long as fourth joint; (the two 



The Ingolf-Expedition. III. ;. 8 



