Il6 CRUSTACEA MALACOSTRACA. III. 



increasing conspicuously in depth from the base to the end, with three spines along the upper and six 

 spines on the lower margin and the end; the first of these latter spines is very short, while the two distal 

 spines, and especially the most distal, are long and moderately thick. Sixth joint with three spines 

 along the distal half of the lower margin. - - Seventh pair (fig. 2 d) have the distal half peculiarly 

 developed; fifth joint is somewhat long and rather strong, with about three stiff setse on the lower 

 margin, while the median part of the upper margin has about six long, fine hairs; sixth joint is un- 

 commonly strong and even a little longer than the fifth, with about four long, fine setae on the lower 

 margin, and about thirteen extremely long, fine setae or hairs along the upper margin; seventh joint 

 moderately long, slender, a little curved and terminating in a slender, somewhat long claw. - - Fifth 

 and sixth pairs rather similar to seventh pair, and especially their sixth joint possesses the same setse 

 along both margins. 



Abdomen somewhat broad (as generally in males of this genus), a little longer than broad 

 (fig. 2 a), tapering a little in breadth from somewhat from the base to near the postero-lateral processes 

 (fig. 2 e), which are moderately large, triangular, acute, directed backwards and somewhat outwards; 

 the posterior margin moderately convex. - - The median lamella of the operculum tapers conspicuously 

 from rather near the base to a little from the end, where each outer margin turns suddenly consider- 

 ably outwards, so that the short terminal part is a little expanded, and the posterior margin of each 

 pleopod is oblique. - - Uropods (fig. 2 e) rather distant from the median line, somewhat less than half 

 as long as the abdomen; basal joint somewhat triangular and moderately small; the exopod tiny, very 

 slender, about as long as the diameter of the endopod. 



Length of the single male 1-85 mm. 



Remarks. This animal is easily distinguished by the shape of the epimera and the fifth 

 segment, and by the legs. First and second pairs of legs are stronger than in D. polituw and some- 

 what similar to those of D. coarctatum (Hansen MS.) G. O. S., but fifth joint of first pair has four spines 

 in D. natator, only three in D. coarctatum. The development of the three posterior pairs of legs, above 

 all the equipment of the upper margin of fifth and especially of sixth joint with very long, thin setse, 

 is hitherto unique in the genus Desmosoma, and these legs show a close resemblance to the corres- 

 ponding legs in the males of Nannoniscus simplex n. sp., N. oblongus G. O. S., N. analis n. sp. or the 

 female of N. inermis, I think that this equipment makes the legs adapted for swimming hence the 

 name D. natator but it is of course impossible to know at present whether these setae also occur 

 in the female. 



Occurrence. Taken by the Ingolf at a deep station in the warm area 



Davis Strait: StaL 36: Lat 6i5o' N., Long. 562i' W., 1435 fath., temp. 1-5; i spec. 



74. Desmosoma laterale G. O. Sars. 

 (PI. XI, figs. 3 a-3 e). 



1899. Eugerda lateralis (Hansen MS.) G. O. Sars, Account, II, p. 254; Suppl. PI. IV, fig. i. 



Female. Head (fig. 33 3 b) somewhat small; each lateral corner before the insertion of the 

 antennula produced into a very conspicuous, oblong-triangular, acute process directed forwards and 



