78 CARL BOVALLIUS, AMPHIPODA HYPERIIDEA. I. 2. HYPERIID^. 



rathei" be looked upon as a kind of cominensalisrnus or syiibiosis, tlic females taking their 

 abode in such animals during the time of repi-odtiction and the young ones resting there 

 until being sufficiently developed to trust their own swimming and feeding powers. Also 

 in Salpai and among the tentacles of Actinife I have observed females and young ones 

 of Hyperia, adult malcs have never, as far as I know, been recorded inhabiting such 

 hospitable animals, but I have many times seen young males, with tolerably developed first 

 pair of antennaj in considerable number hospiting in a large Medusa aurita. Not the females 

 ofall the genera of the family have accepted this mode of living; as far as I have seen in 

 the literature or observed in the nature, it is species of Tauria, Hyperia, Hyperoche 

 and Hyperiella, which have been accustomed to that manner of seeking protection. Some 

 of the species of Euthemisto and Parathemisto, on the other hand, occur in numberless 

 shoals in the Arctic and Antarctic seas, probably not often as fully adult, but as young 

 ones in different stages of development. The tropical species seem to be more scarce, 

 occasionally occuring in company with species of Hyperids, bclonging to other families, 

 or with other pelagic animals. 



From oeconomical point of view some inembers of the family are of great importance 

 as food for herring and other fishes, there are chieflj^ species of the genera Parathemisto 

 and Euthemisto and perhaps also one or another species of Hyperiella in the Ant- 

 arctic region. 



The sexual dimorphismus within the family is distinctly pronounced in the form of 

 the iirst and second pair of antenmv, the multi-articulate flagella belong only to the males ^). 

 Usually the pera3on is broader and wider in the female than in the male. The mandibular 

 palps are just as well developed in the females as in the males. 



The family has rejsresentatives in all the seas round the world, in the Ai-ctic and 

 Antarctic, in the tropical and temperate regions. Its largest representatives, however, 

 seem to be at home in the Arctic, and probably also in the Antarctic region. 



The characteristics which I have found to be most useful for distinguishing the 

 genera within the family are: 

 l:o. The first pair of pera^opoda being simjjle, (Parathemisto, Euthemisto, Phroni- 



mopsis,) suhcheliform (Tauria, Euiulopis, Hyperia, Hyperiella and Themi- 



stella), or cheliform (Hyperoche). 

 2:0. The second pair being simple (Tauria), siibcheliform (Hyperia), or cheliform (the 



seven remaining genera). 

 3:o. Tlie third and fourth pairs forming a folding, prehensile organ (Parathemisto, Eu- 

 themisto, and, more incompletely, Hyperoche), or being comraon walking legs. 

 4:o. The fifth pair being elongated (Hyperiella and Euthemisto), or not longer than 



the two following pairs (the seven remaining genera). 

 5:o. The epimerals being coalesced with the perajohal segments (Themistella and 



Phronimopsis) or free (the other genera). 

 6:o. The body being hirsute (Euiulopis) ov smootk (all the other genera). 



') The questiou on the supposed diiference between Hyperia and Lestrigonus will be discussed under 

 »Hyperia». 



