The genus _Ligia_ agrees with _Ligidium_ alone, in that the flagellum of the larger antennæ has more than ten joints. In both genera, there are no lateral lobes to the head, and the tail appendages are wholly visible from the upper surface of the body. The latter in _Ligia_ is, however, very many times bigger than in _Ligidium_ and shows no abrupt decrease in the width of its segments when the abdomen is reached. =Ligia oceanica= Linné (The Quay-louse). PLATE I. 1767 _Oniscus oceanicus_ Linné (43), p. 1061. 1793 _Cymothoa oceanica_ Fabricius (26), p. 509. 1815 _Ligia scopulorum_ Leach (38), p. 374. 1868 _Ligia oceanica_ Bate and Westwood (1), p. 444. 1898 _Ligia oceanica_ Sars (59), 156, pl. LXX. There is but one British species of _Ligia_, and this, the largest member of the whole tribe to be met with in these Islands, usually attains a length of two centimetres, while adult males may be nearly half as long again. It is the _Oniscus oceanicus_ of Linnæus and lives on the sea shore, where it may be found at low tide beneath stones and rubbish in the crevices of timber. _Ligia_ forms a connecting link between the woodlice proper and the many Isopods which actually live in the sea. The colour of the animals is a greenish grey, and the compound eyes are almost black, so that they are very conspicuous; there are from eleven to fourteen joints to the flagellum of the outer antennae and this feature, taken in conjunction with the large size and habitat, is sufficient to identify the species in question. On the coast of Essex the name "quay-lowders" is given to these crustaceans, "lowder" being apparently an old plural of louse. [Illustration: FIG. 35.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE ANTENNA OF _Ligia oceanica_.] It is worthy of mention that Mr. Webb, when in charge of the Marine Biological Station at Brightlingsea, examined a very large male specimen of _Ligia oceanica_, in which the maxillæ were duplicated and consisted of four pairs instead of two. _BRITISH LOCALITIES:--_ _England_: Brightlingsea; (W.M.W.): Maldon; (W.M.W. from R.M.): Southend; (J.A.M.): Whitstable; (W.M.W.): Herne Bay; Margate; Dover; Folkestone; (J.A.M.) _Scotland_: Shetland to Cornwall; (Norman, 49). _Ireland_: East Coast; West Glengariff; Castletown; Berehaven; Bundoran; (Scharff, 63). _FOREIGN DISTRIBUTION:--_ _Europe_: France; (25): Spain; (12): Denmark; Prussia; Norway; Faroe Islands; Belgium; (59). _Africa_: Morocco; (16). _Genus_--=LIGIDIUM= Brandt, 1833 (3), p. 173. Zia, Koch (34). _Abdomen narrow; habitat, wet moss._