235 
„faunistic principles* (Monard 1919, Thienemann 1920) are also 
applicable to marine communities of animals. For instance: the 
density of Abra alba (41 pr. m 2 ) in contrast to the allied species 
Abra nitida (0,oi pr. m 2 ); the small number of very common spec¬ 
ies, which are not allied at all; the penetration of the animals of 
the Zostera into the Abra-community and of the animals of the 
Abra-community into the Echinocyamus-community. 
Litteratur. 
1. P. Boysen Jensen: Valuation of the Limfjord I. Copenh. 1919. (Rep. 
Danish Biol. Stat. XXVI.) 
2. A. Monard: La faune profonde du Lac de Neuchåtel. Neuchåtel 1919. 
(Buli. soc. neuchåteloise d. sci. nat. 44). 
3. C. G. Joh. Petersen & P. Boysen Jensen: Valuation of the sea. I. 
Copenh. 1911. (Rep. Danish Biol. Stat. XX.) 
4. C. G. J o h. P e t e r s e n : Valuation of the sea. II. Copenh. 1913. Rep. 
Danish Biol. Stat. XXL) 
5. A ug. Thienemann: Die Grundlagen der Biocoenotik und Monards 
faunistische Prinzipien. Basel 1920. (Festschrift f. Zschokke.) 
15-3—21 
