CRUSTACEA MALACOSTRACA. III. 



73 



whole differs much from all genera of the familly. It may be sufficient here to refer to the following 

 description of, and remarks on, the genus. 



PseudomeSUS n. gen. 



Description (the male unknown). Body (PI. VI, figs. 5a — 5b) elongate, slender, round, nar- 

 rowed at the middle about as in Heteromesus ; the integument is somewhat weak. — Head free, some- 

 what ovate, narrowing forwards. Eyes absent. 



Antennulee short (PI. VI, figs. 5 a and 5 c); first joint thick, second joint longer than the first; 

 flagellum very short. Antenna: lost in the specimens excepting the three proximal joints, which are 

 somewhat slender; third joint nearly as long as the two others combined; squama not discoverable. 

 - Mandibles (fig. 5 d) in the main as in Macrostylis ; left mandible with the few teeth on the incisive 

 part thick, the movable lobe short and thick; the setse few in number, but the anterior setae thick and 

 distally ramified; the molar process is short, nearly lamellar, distally very narrow, directed much back- 

 wards and terminating in some setse; palp absent. Maxillipeds (fig. 5 e) nearly as in Nannoniscus; 

 second joint long and moderately broad, twice as long as broad without counting the lobe, which is 

 of very moderate size, longer than broad and at the inner margin terminating in a triangular process; 

 the palp has its three proximal joints moderately broad, fourth joint well developed, about as long as 

 the third, fifth joint somewhat small; epipod long, reaching the middle of third joint of the palp, but 

 almost three times as long as broad. 



Thoracic segments movable, without lateral protuberances. The three anterior segments some- 

 what short, the second a little broader than the first or the third; fourth distinctly narrower than the 

 third, posteriorly somewhat produced and narrowed as in Heteromesus ; fifth segment elongate, much 

 produced and somewhat narrowed forwards; sixth segment much shorter and posteriori} slightlv 

 broader than the fifth; seventh segment a little broader and somewhat shorter than the sixth. — 

 Thoracic legs slender and somewhat long, not differing much in length ; first pair are a little shorter 

 than the second, but agreeing with them and differing from the other pairs in having the fifth joint 

 a little thicker than the third (fig. 5 f ) and armed with a few spines on the lower margin, and their 

 sixth joint is a little thicker than in the following pairs; in all pairs the seventh joint is moderately 

 long and slender, the claw almost setiform; the posterior pairs decrease perceptibly in length from 

 fifth to seventh pair. 



Abdomen distinctly broader than seventh thoracic segment (fig. 5 b), nearly oval, posteriorly 

 broadly rounded ; a first free segment rudimentary. — The female operculum (fig. 5 g) leaves a moder- 

 ately broad lateral part and a rather broad posterior part of the lower surface uncovered. — Uropods 

 small but thick, two-jointed, situated on the ventral side at the antero-lateral margins of the anal 

 doors a little behind the operculum. 



Remarks. Pseudomcsus shows considerable similarity to Heteromesus in fourth and fifth 

 thoracic segments, but it differs very much from the Ischnomesiui in having the head free, not 

 immerged within or fused with first thoracic segment, in the structure of the mandibles, which show 

 much similarity to those in Macrostylis, Nannoniscus and Desmosoma, furthermore in having the two 



The Ingolf-Expedition. III. ;. IO 



