10 
THE VOYAGE OF H.M.S. CHALLENGER. 
branches, which are usually flattened behind, and either angular or rounded on the 
anterior aspect. 
§ a. The zocecia all disposed in alternate series on each side of the front of 
the branches ; the innermost the longest. 
(1) Idmonea atlantica, E. Forbes. 
Idmonea radians, Van Beneclen, Bryoz. de la Mer du Nord, Bull. Brux., xvi. pt. ii. p. 646, pi. i. 
figs. 4, 6. 
? Idmonea coronopus, Defrance, Diet. d. Sci. Nat., vol. xxii. p. 565 ; d’Orbigny, Milne-Edwards, 
Rech. sur les Crisies, p. 23, pi. x. fig. 3. 
Idmonea atlantica, E. Forbes, MSS., Smitt, J.obnst., Gray, Sars, Busk, Ann. and Mag. Nat. Hist., 
ser. 2, vol. xviii. p. 34, pi. i. figs. 6 a-e ; Quart. Journ. Micr. Sci., vol. vi. p. 128, pL xviii. 
fig. 5 ; Rep. Brit. Assoc., 1859 (Trans. Sect.) p. 146 ; (var. tenuis) Brit. Mus. Cat., pt. iii. 
p. 11, pi. ix.; Smitt, Florid. Bryoz., p. 6, pi. ii. figs. 7, 8; Hincks, Waters, &c. 
? Idmonea angustata, d’Orb., Palseont. Frang., p. 731. 
Character. — Zoarium irregularly branched and usually more or less in one plane ; 
branches triangular, one to four or five cells in each series, the innermost the longest ; 
dorsal surface very minutely punctate ; peristome entire, even. Ooecium anterior, 
subpyriform. 
Habitat. — Off Nightingale Island, 100 to 150 fathoms. Station 149e, off Cape 
Maclear, Kerguelen, 30 fathoms. Simon’s Bay, Cape of Good Hope, 18 fathoms. 
[Arctic Seas ; coast of Norway and Finmark ; Shetland ; var. tenuis, North Atlantic ; 
Gulf of Florida, Smitt; Madeira (?) ; Bay of Naples; fossil in Italian Miocene and Canadian 
Post Pliocene (?).] 
(2) Idmonea radians, Lamarck (sp.). 
Retepora radians, Lamk., d’Orbigny. 
Idmonea radians, Busk., Brit. Mus. Cat., pt. iii. p. 11, pi. vii. figs. 1-4; Macgilliv., Nat. Hist. 
Viet., Dec. vii. p. 30, pi. lxviii. fig. 3; Waters; Haswell, Proc. Linn. Soc. N. S. Wales, 
vol. iv. p. 350, vol. v. p. 35. 
1 Hornera radiata, Blainv., Man. d’Actin., p. 419. 
Idmonee rayonnante, M.-Edw., loc. cit., p. 25, pi. xii. fig. 4. 
Character. — Zoarium usually procumbent, radiate in a more or less regular circle, 
stipitate, sometimes suberect, with elongated, straight, subparallel bifurcating branches. 
Branches keeled in front, rounded behind. Dorsal aspect longitudinally sulcate, with a 
series of long perforations or alveoli along the sulci ; the sides and front pitted, some- 
times almost reticulate. Zocecia produced, gently curving forwards, somewhat tapering, 
often with a bilabiate orifice, about (P06 mm. Branches 0'3 mm., series about 0‘4 mm. 
apart. Usually only' one or two zooecia on the sides of the front, alternate, when more 
than one the inner one the longer. Ocecial chambers subglobular on the anterior aspect, 
close below, but not at a bifurcation ; surface coarsely pitted or foveolate. 
