CRUSTACEA MALACOSTRACA. III. 



25 



part, which is longitudinally excavated below (fig. 8 g). — Operculum in both sexes produced consid- 

 erably backwards; its median lamella in the male tapering from the base to the end; and the terminal 

 part of each of its pleopods rather narrow, with the end rounded. — The uropods are very small, 

 consisting of two joints, and one of the rami, probably the exopod, is wanting; they are inserted much 

 in advance of the end of the abdomen on its lateral margins. 



Remarks. Especially by the length of seventh joint of the thoracic legs, the length and shape 

 of the claw and the minute accessory claw, the shape of abdomen and operculum and finally by the 

 reduced uropods this genus is abundantly distinguished from /antra, and by differences especially in 

 the mandibles, the first thoracic legs, the uropods and the male operculum from Pleurogonium. 



Five species have been established; the "Ingolf" has secured two new species. 



10. Ianirella spongicola n. sp. 

 (PI. I, figs. 7 a— 7 c.) 



Description. Closely allied to I. Nanseni Bonn. Body rather convex, scarcely twice as long 

 as broad, measured to the end of the lateral processes. — The frontal process (fig. 7 a) much shorter 

 than in I. Nanseni, only about half as long as the first joint of the antennular peduncle; it terminates 

 in a long spine, and has about two very small spines before the end. No eyes. - The first joint of 

 the antennulae more than twice as long as broad; the flagellum 7-jointed. 



The lateral processes of the head and of the thoracic segments nearly as in / Nansoii, each 

 terminating in a strong, articulated spine and with some thin lateral spines; the only difference as to 

 the processes is that the two processes at each of second to fourth segments are less divergent, and 

 the anterior conspicuously more than half as long as the posterior (comp. fig. 7 b with Bonnier's fig. 1 a). 

 The surface of the body with the same number of processes as in / Nanseni, viz. one on first thoracic 

 segment, two on the head, on fifth to seventh segments and on the abdomen, three processes on second 

 to fourth segments, but all these processes are somewhat or much shorter than in I. Nanseni. Fig. 7 b 

 exhibits the major part af third thoracic segment; it is seen that the median process is only about as 

 long as broad, and terminates in a long, articulated spine, while the submediau intermediate pair of 

 spines are considerably smaller; Bonnier's fig. 1 1 of fourth segment shows the submedian pair several 

 times larger, even larger than the median process. 



The abdomen is more acutely produced (fig. 7 c) than in I. Nanseni and has the end acute or 

 subacute; its four pairs of lateral processes are not, as in that species, subequal in size, btit third pair 

 are conspicuously larger than the second pair, which are distinctly larger than the first or the fourth. 



Length of the largest specimen, a male, 5-5 mm.; a female without marsupium is somewhat smaller. 



Remarks. The differences pointed out between my specimens and Bonnier's elaborate repres- 

 entation of I. Nanseni — especially those in the length of the rostrum and of the dorsal processes on 

 second to fourth segments — are so strong, that I found it necessary to establish a new species 011 my 

 two somewhat mutilated specimens. 



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

 South-West of Iceland: Stat. 81: Lat. 6i°44' N., Long. 27°oo' W., 485 fatli., temp. 6-i ; 2 spec. 



The Ingolf-Expedition. III. 5. 4 



