New material of the genus Echinogammarus belonging to the berilloni-group was collected in the western Pyrenees and north-western Spain. In material from spring regions and caves a new species was found, which in general appearance seems to be intermediate between E. berilloni s.s. and E. aquilifer. A comparative description of the new species is given along with some notes on the ecology of Echinogammarus berilloni.