obtained during the Cruise of fJie ' Oceana.'' 417 



By recent writers the genus Amalopenans of Smith has 

 generally been regarded as synonymous with the earlier 

 Gennadas of Spence Bate *, and it has been suggested f that 

 of the two imperfectly described species referred to the last- 

 named genus by Spence Bate, G. 2)a7'vus, and possibly also 

 G. intermedius, may be specifically identical with A. elegans. 

 Both Ortmann and Faxon J, however, call attention to the 

 important difference in the branchial formulse assigned to 

 these two genera. Amalopeneeus was stated by Smith to 

 possess only one podobranch, attached to the second maxil- 

 liped, in contradistinction to the closely allied Benthesicymus, 

 where five podobranchs are present ; for Gennadas, on the 

 other hand, Spence Bate gives a formula agreeing in this 

 respect with that of Benthesicymus. Ortmann, in recording 

 A. elegans from the Plankton Expedition, states that his 

 specimens agreed with those of Smith in this as in all other 

 respects, and suggests that some error has crept into Spence 

 Bate's formula for Gennadas. This solution of the difficulty 

 might well have been accepted were it not that Alcock §, 

 referring to G. parvus specimens from Indian seas, states 

 that the genus, and by implication this species, does not 

 differ from Benthesicymus in the number of its gills. 



On account of the small size of the present specimen, tlie 

 determination of its complete branchial formula is a matter 

 of some difficulty ; but it can be seen without doubt that 

 it is devoid of podobranchs on the perseopods, and that 

 in so far it agrees with A. elegans and differs from G. parvus. 

 I am unable to point out any other characters of importance 

 whereby it may be distinguished from the last-named species. 

 Spence Bate's figure of the third maxilliped of G. parvus 

 shows the ischial and meral joints subequal in length, while 

 in our specimen, as in Smith's figure, the ischium is nearly 

 twice as long as the merns ; the eye-stalk is not more than 

 one fifth of the length of the carapace (in Spence Bate's 

 figure the proportion is about one third) and is proportion- 

 ately slender, while the whole body is less robust than in the 

 figure. None of these differences, apart from the branchial 

 formula, are sufficient to decide the question of the specific 

 distinctness of the two forms. 



* Am. & Ma{?. Nat. Bist. (5) viii. p. 191 (1881), and Rep. Crustacea 

 Macrura ' Challenger,' p. 339 (1888). 



t Wood-Mason and Alcock, Ann. & Mag. Nat. Hist. (6) vii. p. 189 

 (1801), and Ortmann, /. c. 



X " Stalk-eyed Crust. ' Albatross,' " Mem. Mus. Comp. Zool. Harvard, 

 xviii. p. 208 (1895). 



§ Cat. Indian Deep-Sea Macrura and Anomala, p. 45 (1901). 



Ann. & Mag. N. nist. Ser. 7. Vol, xi. 30 



