Fam. 2. Ianiridae. 



Characters. — General habitus that of the Aselliche, but the lateral parts of 

 the cephalon always lamellarly expanded. Eyes, when present, subdorsal. Superior 

 antenna; sometimes well developed, with the flagellum multiarticulate, sometimes very 

 small, with rudimentary flagellum. Inferior antennae always longer than the su- 

 perior, with the peduncle 6-articulate, and generally carrying a small accessory 

 appendage (scale) outside the 3rd joint. Oral parts normal. Legs subequal in 

 length, with the dactylus generally bi- or tri-unguiculate; 1st pair sometimes differing 

 from the others in being jtrehensile. 1st pair ofMt^epoda in female transformed 

 into a single, large, opercular plate, in male constituting the median piece of the 

 compound operculum, the lateral pieces of which are formed^ by the copulative 

 appendages. The 3 succeeding pairs very delicate, the last pair forming simple 

 smooth lamella?, the 2 preceding ones with the outer ramus narrow and confluent 

 with the basal part. Uropoda biramous, more or less developed. 



Remarks. — The forms belonging to this family resemble the Asellidm very 

 much, as regards their external appearance, and have also hitherto been combined 

 with them. Yet the very different structure of the pleopoda makes it, in my 

 opinion, necessary to place them in a separate family. As additional distinguishing 

 characters may be mentioned the laterally-expanded cephalon, the subdorsal 

 situation of the eyes, the distinctly 6-articulate peduncle of the inferior antenna;, 

 on which, in the greater number of the forms, a small outer appendage, apparently 

 answering to the scale in higher Crustacea, may be distinguished; finally, the 

 more uniform length of the legs, the dactylar joint of which moreover, as a rule, 

 is bi- or tri-unguiculate. All the known forms are exclusively marine, and, as it 

 were, replace the Asellidw in the Oceans. Several genera have been established, 

 amounting to 9 or 10 in all, 4 of which only are represented in the fauna 

 of Norway. 



Gen. 1. Ianira, Leach, 1813. 



Syn: Oniscoda, Latr. 

 ,, Hcnopomus, Kroyer. 

 „ Asellodes, Stimpson. 



Generic Characters. — Body oblong, depressed, with the lateral parts of 

 the segments but slightly produced. Cephalon large, transversely oval, obtuse in 

 front, or with a comparatively small rostral projection. Caudal segment rounded, 



