Ein Beitrag zur Rhombognathinen-Fauna (Halacaridae, Acari) der Bretagne-Kuste. On the French coast of the Channel near Roscoff 18 species of the Rhombognathinae ,vere found, Rhombognathus notops, R. intermedius, R . procerus, R. Subtilis, Isobactrus setosus, I . levis, I. uniscutatus , I. hartmanni, I. rugosus, I. pulchellus, I. tmgttlatus, Rhombognathides seahami, R. pascens, R. mucronatus, R. spinipes, R. merrimani merrimani, R. merrimani needleri, R. brevipes, and Metarhombognathus armatus. The six species Rhombognathis plocerus, R. subtilis, Isobactrus rugosus, I. pulchellus, I. ungulatus, and Rhombognathides brevipes are new to science; the six species Rhombognathus intermedius, Isobactus levis, I.uniscutatus ,I. hartmanni, Rhombognathides mucronatus, and R. spinipes and the subspecies Rhombognathides merrimani merrimani have hitherto not been recorded from the French coast of the Chanel. Five of the six species new to science were collected in the upper midlittoral and supralittoral zone, in a biotop exposed to extreme aridity. It is remarkable that Isobactrus uniscutatus and Rhombognathides spinipes were found only in the estuaries, in areas influenced by fresh water.