occurring on the Norwegian Coasts. 339 



to this genus a new species, (Edicerus novizeaIandio3, and 

 thought that some of the characters which Kroyer ascribed 

 to the genus were of little value as generic characters. To 

 these species Bruzelius has added two, and Sars one, to which 

 a sixth species is now added. Thus so many species are 

 now brought together that the proposed generic characters 

 require a fresh investigation. These species may be divided 

 into two distinct sections, — one of which includes the species 

 saginatus, Kr., affinis, Bruz., lynceus, Sars, and norvegicus, 

 mihi, the other novizealandice, Dana, and obhisus, Bruz. 

 Dana, finding that his (E. novizealandice agreed in some re- 

 spects with (E. saginatus, Kr., especially in the considerable 

 length of the last pair of thoracic legs, by which it was sepa- 

 rated from the genus Iphimedia as he conceived it, assumed 

 therefore that it must belong to the genus (Edicerus, Kr. ; but 

 it, as well as (E. obtusus, Bruz., of which I have had examples 

 from Finmark to examine, differs much from the typical spe- 

 cies. Thus : — In these two species the superior antenna? are 

 elongated, whereas in the other they are very short, only a 

 little or scarcely longer than the peduncle of the inferior 

 antennas. The head does not project in a long and strong 

 rostrum in which the eyes are placed so close together as to 

 look like a single organ, but the rostrum is wanting, and the 

 eyes are, as usual, placed on the sides of the head. The apices 

 of the mandibles are not toothed ; and their palpi, which in 

 species of the same genus are of the same structure, differ in 

 the form of the second joint from those of (E. saginatus. The 

 inner lamella of the first pair of maxilla? is large and furnished 

 with several strongly ciliated hairs, whilst in those of CE. sagi- 

 natus &c. there is only a single seta. There is therefore suffi- 

 cient ground for separating these two forms from each other, 

 especially as each of them includes several species. I have 

 therefore set up (E. obtusus, Bruz., as the type of a new genus, 

 Aceros, mihi, to which I also refer (E. novizealandice, Dana. 

 These two species differ from each other in the length of the 

 peduncle of the superior antennas ; for this, in Dana's species, 

 is short, with a long flagellum, and in (E. obtusus long, with 

 the flagellum short. Lastly, with regard to the place of this 

 genus - in the system, Dana has placed it in the family Gam- 

 maridae, as he only knew his species with long antennae ; but 

 I think that it must go with the preceding genera, as the form 

 of the ovigerous lamellae and their relation to the respiratory 

 plates are the same as in these, whereas those of the genera 

 resembling Gammarus are of a different form. In the struc- 

 ture of the hands on the first two pairs of legs the genus is 

 related to the subfamily Leucothoinae. 



