8 
THE VOYAGE OF H.M.S. CHALLENGER. 
Habitat . — Off Nightingale Island, Tristan da Cunha, 100 to 150 fathoms. 
A beautifully delicate form, distinguishable by its very slender habit and the perfectly 
cylindrical aspect of the branches, with the projecting cylindrical zooecia, the projecting 
portion wholly oral. Its nearest ally would be Crisia holdsworthii. 
Division II.— INARTICULATA. 
Centrifugines emjpdtes d cellules non operculees, d’Orb., Palseont, Fran?., 
p. 605 (pars). 
Inarticulate sen affixe, Bk., Crag Polyzoa, p. 93. 
Incrustata, d’Orbigny, Smitt. 
Character. — Zoarium continuous, not divided into distinct internodes, fixed by a 
contracted calcareous base, either erect and free, or immediately adnate upon foreign 
bodies, and recumbent in whole or in part. 
Subdivision A. ERECTA. 
Family II. Idmoneida:, Busk. 
Tubigeridx (pars), d’Orbigny, loc. cit., p. 698. 
Tubuliporidx (pars), Johnst., Smitt, Hincks. 
Les Tubidijporiens (pars), Milne-Edwards. 
Idmoneidx , Bk., Crag Polyzoa, p. 94; Brit. Mus. Cat., pt. iii. p. 10; Macgilliv. 
Idmoneadx, Bk., Engl. Cyclopedia, art. Polyzoa. 
Ilorneridse, Hincks. 
Character. — Zoarium usually erect and rarely adnate, simple or branched ; branches 
cylindrical, subcylinclrical, or triangular, free or anastomosing. 
The Family here contains the following genera : — 
I. Idmonea, Lamx. 
§ a. The zooecia all disposed in alternate series on each side of the front of the 
branches ; the innermost the longest. 
(1) Idmonea atlanticci, E. Forbes. 
(2) Idmonea radians, Lamk. 
(3) Idmonea marionensis, Busk. 
(4) Idmonea australis, Macgilliv. (PI. Ill, fig. 3). 
(5) Idmonea eboracensis, n. sp. (PI. III. fig. 4). 
