Liga brevis (von Linstow, 1884) Dubinina, 1953, is recorded for the first time in the British Isles.
Detailed descriptions are given of the external features, integument and musculature, excretory system, nervous system and reproductive system of Liga brevis.
The relationship of Liga brevis to other species of the genus Liga Weinland, 1857, settstt Ransom, 1909, is discussed and new information on the relationship of the genital ducts to the longitudinal excretory vessels in Liga facile (Meggitt, 1927) Szpotańiska, 1931, is given. The systematic position of Liga brevicollis (Fuhrmann, 1907) Sandeman, 1959, is discussed. The value of some of the morphological characters used to differentiate the species of Liga is discussed.
A table showing the more important morphological and ecological features of thirteen species ascribed to Liga Weinland, 1857, sensu Ransom, 1909, is given.