Tribe 1. 



HYPERIIDEA. 



Body short and tumid, or very slender, with thin and pellucid integu- 

 ments. Cephalon generally large and tumid; mesosome more or less abbreviate!, 

 with the coxal plates small and subequal in size; metasome powerfully developed, 

 compressed, with large epimeral plates ; urosome depressed, with the 2 outer seg- 

 ments coalesced. Eyes generally enormously developed. Antennae often imper- 

 fect in female, superior ones without any secondary appendage (excepting the 

 genus Hyperiopsis). Oral parts of various structure; maxillipeds without palps, 

 basal lobes coalesced, masticatory lobes divergent, flap-shaped. Gnathopoda not 

 very strong, subsimilar in the two sexes. Pereiopoda of various structure, some- 

 times very dissimilar. Pleopoda powerfully developed. Uropoda more or less 

 laminar, outer ramus of last pair without any terminal joint. Telson simple. - 

 Parasitic on pelagic animals, especially Medusae. 



Remarks. - - This is a rather anomalous division of the Amphipoda. 

 which by most authors has been placed at the close of the order. I think, 

 however, it will be more appropriate to follow Boeck in treating of the 

 present group at the head of the order, placing the typical Amphipoda 

 (Gammaridea) in the midst between this tribe and that of the Caprdlidea, the 

 latter constituting a far more distinctly degradated type. 



Fam. 1. Hyperiidae. 



Cephalon large and deep, almost globular. Eyes occupying the ent in- 

 lateral walls of the head, visual elements very numerous and elongated, radiat 

 ing from a central pigmentary mass. Both pairs of antenna' with distinctly 

 triarticulate peduncles, the inferior ones originating each t'nmi a large ami 

 immobile basal joint, nagellum of both pairs in female comparatively slmrt 

 and non-articulated, in male very slender and elongated, multiarticulate. Kpi- 

 stome not projecting. Anterior lip with a large bilobed bmval plate covering 



