Observations sur le genres Neojordensia Evans et Orthadenella N.G. en Europe occidentale (Gamasides. Dermanyssina, Ascidae). - During the course of а two уеаг microarthropod sampling of soil and litter of ап old pasture in Normandy, it was established that the individuals of ’Neojordensia levis’ originating from the litter layer actually belong to three distinct species. Neojordensia lawrencei Evans (= Lasioseius berlesei (Ouds.) sensu Westerboer = L. frondeus Karg) was also examined then in order to assess the phylogenetical relationships between the last species and the three first ones. These relationships are far from being tlle genus tie. The family Ascidae is clearly delimited; it is indeed necessary to define correctly the familial sets within the соЬ. Dermanyssina in view of systematic investigations. Several additions are supplied to the generic definition of Neojordensia Evans; that of Orthadenеиа п. g. (type species Neojordensia lawrencei Evans) is provided. Тhе main morphologiral differences between these two genera are listed (Table 1), as weH as their similarities (see « Discussions ») which are shown to Ье of convergent nature. А brief review of previous taxonomical treatments of tlle two genera is given. Two new Neojordensia species are described. Data оп geography and habitats of the various taxa under study are supplied. Тhе simultaneous occurence of tlle three Neojordensia spe<;ies in tlle litter of tlle same grascland is discussed, as well as, some peculiarities of their seasonal dynamics during tlhe sampling period.