Tribe 1. 



HYPERIIDEA. 



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

 ments. Ceplialon generally large and tumid ; mesosome more or less abbreviated, 

 with the coxal plates small and siibequal in size; metasome ])owerfully developed, 

 com])ressed, with large epimeral ])lates ; urosome depressed, with the 2 outer seg- 

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

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

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

 basal lobes coalesced, masticatory lobes divergent, tiai)-shaped. Gnathopoda not 

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

 times very dissimilar. Pleopoda 2}owerfully developed. TJro])oda 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 gi'oup at the head of the order, placing the typical Amphipoda 

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

 latter constituting a far more distinctly degradated type. 



Fam. 1. Hyperiidae. 



Cej)halon large and deei), almost globular. Eyes occupying the entire 

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

 ing from a central pigmentary mass. Both pairs of antennae witli distinctly 

 triarticulate peduncles, the inferior ones originating each from a large and 

 immobile basal joint, flagellum of both pairs in female comparatively short 

 and non-articulated, in male very slender and ehmgated, multiarticulate. E])i- 

 stome not ])rojecting. Anterior lip with a large bilobed buccal plate covering 



