CRUSTACEA MALACOSTRACA. III. 



33 



1 6. Hydroniscus abyssi n. sp. 



(PL II, figs. 5 a- 5 k). 



Female. Body three times as long as broad, broadest considerably behind the middle; its 

 surface extremely smooth. — The frontal process of the head (fig. 5c) about as long as broad; its end 

 broadly rounded: the antero-lateral augles are triangularly protruding. -- Antennulse with the flagellum 

 5-joiuted; the terminal joint very short. -- Antennae somewhat longer than the antennulse; the proximal 

 joints of the peduncle are very difficult to discern, being placed in a deep excavation limited by the 

 very high lateral plates of the head; last joint of the peduncle longer than the preceding joint; flagel- 

 lum nearly as long as the peduncle, 9-jointed. 



The abdominal operculum a little longer than broad (fig. 5k, 0); with a rounded median keel 

 not reaching the base; the terminal margin somewhat short, almost straight. Seen from below (fig. 5k) 

 the anal doors (a) are very conspicuous and reach the hind margin, and near the outer margin of each 

 door the postero-lateral process (/) is observed. 



Length of the largest specimen, which has no marsupium, 2*8 mm. 



Remarks. This interesting species is easily distinguished from all marine Isopoda hitherto known. 



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



South-West of Cape Farewell: Stat. 38: Lat. 59°i2' N., Long. 5i°c>5' W., 1870 fath., temp. 13 ; 



7 spec, most of them very young. 



Group III. Munnini. 



Body very varying in aspect, but the four anterior thoracic segments conspicuously marked off 

 from the three following segments, and second to fourth segments considerably to very much broader 

 than abdomen, which is less or more produced. Head free. Eyes, if present, situated on lateral pro- 

 tuberances or processes of the head. Antennse with the squama minute or wanting. — Mandibles with 

 the incisive part, the movable lobe, and at least a few setse well developed; molar process directed 

 somewhat or even considerably forwards, either shaped nearly as in Ianira or longer and conspicuously 

 thinner with the end oblique; palp in some genera reduced or wanting. Maxillary palp with second 

 joint from rather broad to slender; the two distal joints well developed. - ■ Thoracic segments movable. 

 First pair of legs prehensile, their fifth joint being spiniferous and at least robust, frequently much 

 thickened. The six following pairs "more or less rapidly increasing in length, simple, ambulator}"; 

 accessory claw generally discernible, sometimes long and strong [Munna). - - Uropods always situated 

 on or above the lateral margins, and somewhat or considerably in front of the end of abdomen, 

 generally minute and submarginal, but in a few forms strong, long, and with their insertions subdorsal. 



Remarks. The group answers to the family Munnidse G. O. Sars. The "Ingolf gathered 

 three of the four genera represented in the "Account" of Sars, and instead of the fourth genus, Para- 

 munna G. O. S., it has secured a new genus, Pseudomunna n. gen. In reality some of the genera, as 

 Munna and Dendrotion, differ much from each other in a number of features. And gradually several 



The Ingolf-Expedition. III. ;. 3 



