78 CARL B0VALL1US, AMPHIPODA HYPERIIDEA. I. 2. HYPERIID^. 



rather be looked upon as a kind of commensalismus or synbiosis, the females taking their 

 abode in such animals during the time of reproduction and the young ones resting there 

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

 in Salpa? and among the tentacles of Actinias I have observed females and young ones 

 of Hyperia, adult males 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 antennae in considerable number hospiting in a large Medusa aurita. Not the females 

 of all 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, belonging to other families, 

 or with other pelagic animals. 



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

 as food for herring and other fishes, there are chiefly 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 first and second pair of antenna?, the multi-articulate flagella belong only to the males 1 ). 

 Usually the perason 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 representatives in all the seas round the world, in the Arctic 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 peraeopoda being simple, (Parathemisto, Euthemisto, Phroni- 



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



stella), or cheliform (Hyperoche). 

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



seven remaining genera). 

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

 themisto, and, more incompletely, Hyperoche), or being common 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 peroeonal segments (Themistella and 



Phronimopsis) or free (the other genera). 

 6:0. The body being hirsute (Euiulopis) or smooth (all the other genera). 



J ) The question on the supposed difference between Hyperia and Lestrigonus will be discussed under 

 »Hyperia». 



