KONGL. SV. VET. AKADEMIENS HANDL1NGAR. BAND. 22. N:0 7. 143 



After summing up and valuing the characteristics of all the above enumerated spe- 

 cies we have thus left fifteen good species and two doubtful ones, which follow here 

 in chronological order: 



Hyperia medusarum, 0. F. Muller, ?Ii. mediterranea, Costa, 



H. galba, Montagu, ?H. minuta, Th. Edward, 



H. Latreillei, H. Milne Edwards, H. bengalensis, Giles, 



H. Fabrei, H. Milne Edwards, H. sibaginis, Stebbing, 



H. Gaudichaudii, H. Milne Edwards, H. luzoni, Stebbing, 



H. fera, Dana, H. promontorii, Stebbing, 



H. Danae, n. n., H. dysschistus, Stebbing, and 



H. agilis, Dana, H. schizogeneios, Stebbing. 



H. Normani, n. n., 



To this number I am adding the descriptions of some new species, Hyperia hy- 

 strix, H. spinigera, H. crucipes, H. thoracica, H. latissima, and H. Gilesi. 



The sexual difference within the genus is shown: 



1. In the general form of the body, the males being more slender and having the hind 

 part of the body comparatively longer. 



2. In the length of the head, the head of the female being usually somewhat shorter 

 and broader than that of the male. 



3. In the form of both pairs of antennas, those of the males being more or less elong- 

 ated and provided with a multi-articulate flagellum, those of the female being short 

 with the flagellum composed of one or very few joints. I may venture the supposition 

 that this reduced form of the female antennae is connected with the habit which 

 the females, at least of most species of the genus Hyperia as well as of other 

 genera of the family, have of living within yellowfishes or other pelagic animals. 



4. In the form of the uropoda, those of the female being often somewhat shorter than 

 those of the male. 



Among the species of Hyperia we find many with some of the peraeonal segments 

 coalesced on the dorsal side. At first I believed that this feature depended upon the age 

 of the animals in question, supposing those with coalesced peraeonal segments to be young 

 and not fully developed individuals. But a further investigation into the matter has 

 made me inclined to look upon them as adult animals, and, at least with regard to some 

 of them, as good species. The reasons why I think so are: 



1. The young ones of species of Hyperia, with seven free peraeonal segments, as for 

 instance H. medusarum, H. Latreillei, H. spinigera and H. Gaudichaudii, have 

 when leaving the egg seven distinct peraeonal segments, the sutures between the seg- 

 ments being plainly visible on the dorsal side as well as at the lower margin of the 

 peraeon. 



