A new species, Philosyrtis aegusae sp. nov., collected in the ‘Otoplanen-Zone’ of the sands of western Sicily, is described. The specimens show the typical morphological peculiarities of the subfamily Parotoplaninae (‘Turbellaria’: Otoplanidae), but differ clearly from the species already described. The body length of the sexually mature animals reaches 0.9–1.1 mm and they appear to belong to the genus Philosyrtis because of the general arrangement of testes and germo-vitellaria, and of the sclerotic apparatus. The vesicula granulorum is clearly distinct from the sclerotic apparatus unlike the other ten species belonging to the same genus. The male copulatory organ consists of a dorsal group of 7–8 spines similar in shape and length (33–40 mm), and a ventral group of at least 6 long thin spines with curved pointed tips. The new species differs from the already described species above all in its body dimensions, the shorter path of the vitellaries and especially the characteristics of the male sclerotic apparatus.
