THE AMPHIPODA. 35 



But the effect of admitting Ei/perla sibaginis into the genus Hyperioides will be to deprive 

 that genus of one of its most striking characters, " eves occupying only the upper 

 part of the head." For the figure in the ' Challenger ' Eeport, which bas the indepen- 

 dent guarantee of Dr. Bovallius, sliows the eyes covering the cheeks as usual in 

 Hi/perla. In B. longipes there is always a considerable part of the cheek on which no 

 ocelli are abutting. Unless, therefore, the figure of the Pacific form is erroneous, this 

 disposition of the ocelli will furnish an important specific distinction, but cannot be 

 retained in the definition of the genus. 



The front of the head is blunt, so that there is no question of a rostral prolongation 

 in advance of the first antenna3, and the projection apparent in lateral view is almost 

 confined to the male, the head in the female being on the wdiole strongly truncate in 

 front, presenting, as Dr. Vosseler says, " in lateral view a form quite unusual for a species 

 of Syperia, that of a genuine tete carree." 



18. Hyperioides longipes, Chevreux. 



1900. Hyperioides lonyipes, Chevreux, Amphipodes de I'Hirondelle, p. 143, pi. 17. fig. 2, 



1901. Hyperioides longipes, Lo Bianco, Mittheil. Stat. Neapel, vol. xv. pp. 422, 447. 



1901. Hyperia sibaginis, Vosseler, Amphipoden der Plankton-Expedition, p. 60, pi. 7. figs. 6-20 



(Parahyperia ? , p. 56, Hyperia sibaginis var. longipes, or Hyperia longipes, p. 63). 

 1903. Hyperioides longipes,' A.. 0. Walker, Ann. & Mag. Nat. Hist. ser. 7, xii. p. 229, pi. 19. figs. 7-13. 



Excellent figures and descriptions of the species have been given by M. Chevreux, 

 Dr. Vosseler, and Mr. A. O. Walker, F.L.S. The only addition of importance to insist 

 on is the circumstance already noted that in the female the mandible is without a palp. 

 Dr. Vosseler, in describing the female, speaks of the mandibles as having a three-jointed 

 palp, but he gives references to figures of the mandible which in the explanation of his 

 plate are attributed to a male. It may be inferred, therefore, that identity of the mouth- 

 organs in the two sexes was presumed by him, as it had been by M. Chevi-eux in defining 

 the genus. Claus, in ' Die Platysceliden,' p. 3 (1887), contrasting " die Hyperinen " with 

 " die Gammarinen," says boldly of the former that " the mandible carries a three-jointed 

 palp only in. the male sex." In response to this. Dr. Bovallius (Mon. Amph. Hyperiidea, 

 p. 158, 1889) declares that in the female of Hyperia medusarum (O. F. Midler), called 

 H. spinipes by Boeck, the mandibles arc exactly like those in the male, but a little more 

 robust, and he gives a drawing of these organs in the female of this typical species on 

 purpose to show the three-jointed palp. This palp is present likewise in the female of 

 Syperia galba (Montagu). On the other hand, in the three ' Challenger ' species Hyperia 

 luzoni, H dysschistus*, and H. schizogeneios, the females show no mandibular palp, and 

 this is tlie case also in the two species recently described by Dr. Vosseler as H. macro- 

 phthalma and H. hydrocephala. The last-named author suggests that such species should 

 be grouped in a subgenus. lie has further observed that in U. Fubrei, Milne-Edwards, 

 the mandibles of the female are variable, sometimes having no palp and at others one 

 that is small and uniarticulate. 



* A. 0. Walker now identifies this with Hyperia bengahnais (Giles), in ' Report on the Amphipoila collected by 

 Professor Herdman at Ceylon,' p. 235 (1904). 



SECOND SERIES.— ZOOLOGY, VOL. X. 7 



