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 Beneden, Bryoz. de la Mer du Nord, Bull. Brux., ivi. pt. ii. p. 646, pL i. 

 figs. 4, 6. 

 1 1dmonea coronopus, Defrance, Diet. d. Sci. Nat., vol. xxii. p. 665 ; d'Orbigny, Milue-Edwards, 

 R^ch. sur les Crisies, p. 23, pi. x. fig. 3. 

 Idmonea atlantica, E. Forbes, MSS., Smitt, Johnst., Gray, Sars, Busk, Ann. and Mag. Nat. Hist., 

 ser. 2, vol. xviii. p. 34, pi. i. figs. 6a-e ; Quart. Journ. Micr. Sci., vol. vi. p. 128, pi. 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. 

 1 1dmonea angustata, d'Orb., Palseont. Fiang., 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 Grood Hope, 18 fathoms. 



[Arctic Seas ; coast of Norway and Fiamark ; 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. II, pi. vii. figs. 1-4; Macgilliv., Nat. Hist. 

 Vict., Dec. vii p. 30, pi. Ixviii. fig. 3; Waters; Haswell, Proc. Linn. Soc. N. S. Wales, 

 vol. iv. p. 350, vol. V. p. 35. 

 tJEornera 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 0"06 mm. Branches 0"3 mm., series about 0"4 mm. 

 apart. UsuaUy only one or two zocecia 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. 



