On a collection of 
Gammarus from Randers Fjord, Denmark. 
By 
K. Stephensen. 
(Con ications from the Department of Arthropods of the Zoological Museum, 
Copenha . — No. 2). 
With 9 figures. 
(Communicated at the meeting on Novbr. 24th 1916). 
Among a considerable material of Invertebrata from. Randers 
Fjord, collected by Dr. A. C. Johansen and Mr. Hj. Ussing, with 
a view to showing the variation of the fauna from the mouth of 
the fjord to the head, especially in regard to the salinity)”), a 
sréat many specimens of Gammarus were also found. The mate- 
rial contained the following species: G. pulex L., G. locusta L., G. 
Zaddachi Sexton (new to Denmark), an intermediate form between 
G. locusta L. and G. Zaddachi Sexton, thus showing that G. Zad- 
dachi is not a good species, and G. Duebenii Lilljb. (new to Den- 
mark). Thus there were all the species hitherto known from Den- 
mark except G. marinus Leach, but in return two ,species" were 
new to Denmark. 
Ås the salinity in the fjord varies from 0% in the inner parts 
to 24 900 at the mouth at the bottom and 18% at the surface, 
the species vary a great deal according to the environment. 
The following pages will serve to show that also the specific 
characters are s0 vague that it is most probable that all the species 
In reality are one species. 
Already 1877 in his paper Gristacea Daniæ (Naturhist. 
Tidsskrift, ser. 3, vol. 11, 1877, p. 123) Meinert considers G. 
Duebenii and G. marinus varieties of G. locusta; but his reason 
v This paper, with the title ,,Randers Fjords Naturhistorie, ved Dr. A. C. 
Johansen", is now going to the press. 
