EEPOET ON THE ISOPODA. 



Tribe I. ASELLOTA. 



The group Asellota may be divided as follows : — 



A. Posterior thoracic appendages similar in structure to anterior. 



1. ASELLID.E. 



B. Posterior thoracic appendages natatory with dilated penultimate and anti- 

 penultimate joints. 



2. Munnopsid^e. 



Family Asellid^e. 

 Janira, Leach. 



Janira, Leach, Edin. Encycl., vol. vii. p. 434. 



Eenopomus, Kr0yer, Naturhist. Tidsskr., Ek. 2, Bd. ii. p. 380, 1849. 



Oniscoda, Latreille, Eegne Animal, vol. iv. p. 141. 



Asellodes, Stimpson, Marine Invert. Grand Manan, 1853, p. 41. 



This genus does not differ very much from Jsmxi. The main points of difference are 

 in the antennae ; the first pair of antennae have a much longer flagellum and the second 

 pair are distinguished by the possession of a rudimentary exopodite in the form of a 

 setose scale attached to the outer margin of the third joint. As a general rule the first 

 pair of thoracic limbs are prehensile in character, but according to G. 0. Sars this is not 

 the case with the female of Janira breviremis ;* the uropoda are as a rule longer and better 

 developed than in Jsera. The mandibular palp is stated by Westwood and Spence Bate 2 

 to be absent, though with a certain reservation, in Janira maculosa; it is present in a new 

 species to be presently described {Janira abyssicola) which in other respects presents a 

 structure characteristically like that of Janira. 3 In the mean time it is evidently advisable 

 to retain the genus Janira as distinct from Jmra on account of the different form of the 

 antennas, which is undoubtedly the only well marked character that can be made use of. 



One species of Janira that will presently be described is interesting on account of its 

 coming from deep water, 1350 fathoms; this species, which I have named Janira 

 abyssicola, is not by any means unlike the typical forms of the genus, only differing from 

 them in the total absence of eyes. This difference, evidently resulting from a difference 

 of habitat, is not to my mind sufficient to distinguish this species generically, though in 

 many instances, e.g., Pleurogonium, the absence of eyes does imply a generic distinction. 



1 Vifcnslc. SeUh Forhandl, 1882, p. 64. 2 British Sessile-eyed Crustacea, vol. ii. p. 336. 



3 Through the kindness of the Rev. T. R. R. Stebbing I have been able to examine a specimen of Janira 

 maculosa, and find that it has a distinct three-pointed palp. 



