During a short trip in the western part of the Pyrenees in August 1968 many samples of Gammaridae were collected both on the French and Spanish slopes of this mountain chain. Most of the specimens collected appeared to belong to the species Echinogammarus berilloni (Catta, 1878), or to closely related forms, but likewise it became clear that there exists a great morphological diversity in this group ofE. berilloni. This diversity, often called variability, was noticed already by Spandl ( 1926 ) and Margalef ( 1956 ) and made a more detailed study desirable. A great difficulty is the absence of a good and detailed description and trustworthy figures ofE. berilloni. The following published figures may serve as a basis for recognition of this species : Catta, 1878, fig. 1. Chevreux, 1896, figs. 1, 2, 3. Spandl, 1926, figs. 1, 2, 3, 4. Margalef, 1956, figs. 1, 2 (for subspecies calvus). Hoffmann, 1963, figs. 29 – 37.