CRUSTACEA MALACOSTRACA. IV. 57 



minute saw-teeth, and the posterior part of this margin is, as already mentioned, armed with strong and 

 closely set teeth rapidly increasing in length to below the insertion of the antennulse. Free thoracic segments 

 rather considerably shorter than the carapace; last segment with two pairs of sublateral denticles, and some- 

 times also a pair of denticles on fourth segment; postero-lateral angle of last segment scarcely produced. 

 Abdomen somewhat slender; the two anterior segments each with a pair of sublateral denticles, and some- 

 times also a pair of denticles on fourth segment; fifth segment long, almost twice as long as the sixth, with 

 about four pairs of sublateral denticles on its posterior third; sixth segment with a pair of sublateral denticles 

 near the posterior margin. 



Antennula? (fig. 4 a) very long, as the peduncle is almost as long as pseudorostrum ; its first joint 

 seen from below about as long as the second, with a somewhat long tooth below and a similar tooth on the 

 inner side at the end; third joint somewhat shorter than the second; upper flagellum considerably shorter 

 than third peduncular joint, 3-jointed; lower flagellum shorter than first joint of the other flagellum, 3-jointed. 

 Antennae with a thin and moderately long, plumose seta on the end of the terminal joint; mandibles as in 

 Diastylis sens. Sars. Third pair of maxillipeds normal; second joint a little broader and proportionately 

 shorter than in I>. Rathkii, and armed with several teeth along the distal part of its inner margin; ischium 

 with a tooth on the inner margin, and merus with a tooth below; the long proximal joint of the exopod 

 without teeth. First pair of legs (fig. 4 b) moderately long, stretched forwards reaching scarcely to the end 

 of the antennular peduncles; second joint with about 7 strong teeth on the distal half of the inner margin 

 and the same number of teeth below near the outer margin; propodus a little shorter than the carpus and much 

 longer than the dactylus; the long proximal joint of the exopod with a number of teeth on the middle part 

 of its outer margin. Second pair of legs (fig. 4 c) a little more than half as long as first pair; second joint with 

 a few teeth on the inner margin and some teeth on the lower side ; ischium with a somewhat small tooth on 

 the inner corner; carpus about twice a long as the dactylus; the long proximal joint of the exopod with 

 fine teeth on half of the outer margin. Third and fourth pairs of legs without exopods; fourth pair (fig. 4 d) 

 with the carpus about twice as long as the two distal joints together. — Uropods somewhat long; peduncle 

 in the adults almost as long as the two posterior abdominal segments together, with 6 or 7 spines on the inner 

 margin ; in subadult specimens without marsupium or with its plates small the peduncle is somewhat shorter 

 (fig. 4 e) than the two abdominal segments together and with 6 marginal spines ; rami long, as the exopod 

 is only somewhat shorter than the peduncle and somewhat or rather little longer than the endopod, which 

 is slender, 3-jointed, its first joint as long as the two distal joints combined, with 6 or 5 marginal spines in 

 the adult, 5 or 4 such spines in subadult specimens; second joint longer than the third and with 2, or in the 

 adult ], marginal spines. Telson not much shorter than the peduncle of the uropods; its slender part is con- 

 spicuously longer than the thickened proximal portion, with 5 pairs of lateral spines; the terminal spines 

 are longer and thicker than the lateral ones. 



Length of the females with marsupium 6 mm. 



Remarks. This interesting species is a typical Diastylis, excepting in having the pseudorostrum 

 extremely long, even proportionately longer than in any other species of the order. 



Occurrence. Gathered by the "Ingolf" at two deep stations in the warm area. 



The Ingolf Expedition. III. 6. 8 



