Summary. 



1) Through the researches carried out a not inconsiderable nuinber of forms 

 have been shown to exist in Oresund tbat had not before been met with there, 

 but had only been known from tbe Skager Rak or Kattegat; a smaller number are 

 unknown in these sea-districts. 



2) The fauna of the Oresund district, as regards vertical distribution, may be 

 divided into a littoval fauna, poor in species, and a far richer sub-littoral fauna. 

 The lower limit of the littoral fauna practically coincides with tbe 20-metre curve. 

 The fauna is on the whole identical with what C. G. Joh. Petersen cbaracterized 

 as the Macoma-community. The littoral forms are alrnost without exception present 

 at least in tbe west part of the Baltic Sea, several extending far into that district. 

 The sub-littoral fauna inhabits the deeper parts (20 — 50 metres) of the Sound and 

 consists of forms which seldom and as a rule only in solitary examples are met 

 with in the west part of the Baltic Sea. The species Diastylis rathhii and Michthei- 

 mysis mixtet, which oeeur in quantities, constitute exceptions to this. The sub- 

 littoral fauna inhabits for the most part the clay bottom and, as regards its com- 

 position, may be identified with Petersen's Haploops-community. 



3) As a result of bathymetric and hydrographic conditions, a sharply marked 

 alteration in tbe character of the fauna takes place in the neighbourhood of Ven, 

 at the line Landskrona — Vedbaek. North of this the sub-littoral fauua is present, 

 but southwards for the most part only the littoral fauna can be traced, and this 

 also is more richly developed north of Ven. 



4) A closer examiuation of the composition of the fauna north of the Lands- 

 krona — Vedbaek line shows that the fauna of the east of the Kattegat can be ob- 

 served, in an essentially unaltered State, down to the limit mentioned, while again 

 a number of the species characteristic of the west of the Kattegat are absent or 

 only seldom found. 



This far-reaching consistency in the sub-littoral fauna is made possible by the 

 prevailing harmony in the hydrographic conditions, as shown by Danish researches. 

 The parts of the Sound lying below 20 metres may on the whole be said to present 

 the sarae conditions in temperature and saltness as the east of the Kattegat south 



