18 THE VOYAGE OF H.M.S. CHALLENGER. 



The uropoda (PI. IV. figs. 13, 14) are rather peculiar in shape, and recall those of 

 Iantlwpsis bovallii ; the distal joint is extremely lung and curved, both its margins ar< 

 furnished with numerous long simple hairs; the endopodite is proportionately very 

 short, though considerably larger than the minute exopodite. 



Station 153, in vicinity of the Antarctic Ice, February 14, 1874; lat, (55° 42' S., 

 long. 79° 49' E.; depth, 1675 fathoms; bottom, blue mud. 



Jsera, Leach. 



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



Jxridina, Milne-Edwards, Hist. Nat. des Crust., vol. vii. p. 150. 



Oniscus, Montagu. MSS. 



Asellus, Packard, Mem. Bost. Soc. Nat. Hist., vol. i. 1867, p. 29G. 



Milne-Edwards in his Histoire naturelle des Crustace's J separated the species Jsera 

 nordmanni as a distinct genus under the name of Jseridina, but, as has been pointed 

 out by Westwood and Spence Bate, 2 the distinction between the two genera, viz., the 

 form of the abdominal operculum, is in reality only a sexual difference, and the name 

 Jsera must therefore be retained as having the priority. Several species of the 

 genus have been described, but many of them rest on insufficient data, and it is a 

 difficult matter therefore to decide how many species should be admitted. As well- 

 characterised species may be mentioned, Jsera albifrons and Jxra nordmanni, the 

 differences between which have been clearly pointed out by the Rev. T. R. R, Stebbing. 3 

 Jsera wahishiana of Spence Bate 4 appears to be perfectly distinct ; Jsera marina, Jsera 

 krbyeri, and Jsera baltica are supposed to be merely synonyms of Jsera albifrons; the 

 second of these is figured in the illustrated edition of Cuvier's Rep-ne Animale. 5 



A species described by Lucas 6 under the name of Jsera longicornis, but figured by 

 him in the same work as Jsera deshayesii, appears to me to be wrongly assigned to the 

 genus Jsera. It agrees with Janira in the form of the antennary organs, in the prehensile 

 character of the first thoracic appendages, and in the elongated biramose uropoda. This 

 species is considered by Heller 7 to be identical with Grube's 8 Jsera JUicornis. 



An American species {Jsera copiosa), described originally by Stimpson, is declared by 

 Harger 9 to be identical with Jsera albifrons. This author discusses the synonymy of 

 other species, and arrives at the conclusion that besides the species mentioned above, Jsera 

 nivalis, Jsera maculata, and Jsera gronlandica (Packard) are probably varieties of Jsera 

 albifrons. 



1 Tome iii. p. 149. 2 British Sessile-eyed Crustacea, vol. ii. p. 321. 



3 Ann. and Mag. Nat. Hist, ser. 4, vol. xvii. p. 80, pi v. 4 Proc. Zool. Soc. Lond., 18G4, p. 667. 



6 PL Lxx. fig. 1. » Exploration Scientifique de l'Alg&rie, t. i. p. 66; t. iv., pi. vi. fig. 4. 



7 Verhandl. d. k. k. zool.-bot. Gescllsch. Wien, 1866, p. 733. 8 Die Insel Lussin, p. 75. 



9 Marine Isopoda of New England, U.S. Comm. of Fish and Fisheries for 1878, Washington, 1880, p. 315. 



