The following is the first instalment of an investigation on the structure and systematic relations of the Actiniae collected by one of us in Torres Straits. We decided to publish our account of the Zoanthese first, as it is a well circumscribed group and admits of independent treatment. We took this opportunity of studying the British forms, and have thus had a considerable number of forms under examination at the same time. This has given us a personal knowledge of every genus except Mammilifera, of which genus no authentic specimens exist in any museum. Our account of the British Zoantliese is simultaneously published with this as " A Revision of the British Actiniae," Part II. : The ZoanthejB (Trans. Roj^al Dublin Society, vol. iv., ser. ii.) ; and we would refer the reader to that Memoir for a general summary of the anatomy of the group, and a special account of that of the British representatives. We have also given a classification of the Zoanthese, and as far as is possible have allocated all the species described by other authors to their proper genera. It is impossible at the present time to monograph this group, as there is such a general sameness in external character that it makes it difiicult to seize on points which are of descriptive value. The present confusion in which this group lies is mainly due to this fact ; the fault is that of the animals themselves rather than that of the zoologists who have described and named them. This similarity of appearance not onlj^affects the species of a genus, but also the species of different genera. Thus it becomes a necessity for every species to be examined anatomically by means of microscopical sections, first to determine its genus, and secondly to discover accurate specific characters. Once a species is thoroughly TKANS. ROY. DUB. SOC, K.S. VOL. IV., PART Xnt. 5 E Reports on the Zoological Collections made in Torres Straits, 1888-1889. Ciivier (1798) was the first to recognise some distinction between the Zoanthese and other Actinia, but in an indefinite sort of way; he refers to " 1. Le zoanthe k cinq pdtales [Actin. diantlms) ; 2. Le zoanthe k drageons {Actin. sociata^r Lamarck (Systfeme, 1801) first divided the Actinse into the genera Actinia and Zoantha ; he says (1801, p. 363): " ii''. genre. Zoanthe, Zoantha Zoantha sociata, Act. sociata, Sol. et Ellis, Hydra sociata, Gmel." Bosc (180S, p. 261) refers to " Zoanthe, Zoantha, Lam. ; Z. ellisii; Hydra sociata ; Act sociata, S. & Ell." Cuvier, in 1817 (p. 53), speaks of Zoantlms sociatus. In Deshayes and Milne-Edwards' revised and augmented edition of Lamarck's Hist, des anim. sans vert. (1836, 2nd ed., p. 77), three species are acknowledged: "Zoanthe (Zoantha).-1. Zoantha ellisii, Bosc {^Act. sociata, etc.); 2. Zoantha solanderi, Les. ; 3. Zoantha hertholetii, Ehr." Dana is the only later author who adheres to Zoantha instead of Zoauthus. According to the generally accepted rules of zoological nomenclature the Greek av6o<; would have to be written anthiis, it being agreed that, "in writing zoological ...