120 
together with the species found by former investigators. Hereto 
shall be added 4 Harpacticidae and 3 Ostracoda. Altogether 39 
fresh-water Entomostracians are known from Iceland. Four of the 
species found by me are new to Iceland, namely Laihonura recti- 
rostris, Lynceus guttatus, Lynceus quadrangularis and Lynceus inter- 
medius. 
Ecologic Investigations. 
The main factors with which I have dealt in this part of the 
paper, are the height above the sea-level and the density 
of the vegetation. 
As to the height above the sea-level, I have divided the localities 
into three groups, viz: 
Gr. I, 0—100 m, the waters icefree during about 158 days. 
„ II, 101—300 m, „ „ „ „ „ 137 „ 
„ III, over 300 m, „ „ „ „ „115 „ 
To gr. I belong the localities along the coast, while gr. III con- 
tains the great heaths in the inner highland; gr. II is a transition 
between the two other groups. 
I have besides classified the waters, according to their vegetation, 
in three groups, viz: 
Gr. 1, no vegetation. 
„ 2, scarce vegetation. 
„ 3, dense vegetation. 
I have as far as possible divided gr. 3 into two sub-groups, 
a. containing the Helophyts (in sensu Raunkiær), b. containing the 
Hydrophyts, because the Helophyts do not in the same degree as 
the Hydrophyts fill up the water. As shown in the table p. 91, 
the density of the vegetation is diminishing with the increasing 
heights above the sea-level. 
The Distribution of the Species in Relation to the Height 
above the Sea-level. 
In gr. I 26 species are found, in gr. III 23 species. Thus the 
number of species has only decreased a little, and, as Tab. 5 shows, 
a diminuation of the number of individuals does not at all take place. 
