196 IDMONEID&. 
Genus, MARGARETTA—Gray. 
Cells disposed in four rows, back to back, each pair facing at right ~ 
angles to those above and below ; furnished with long bristles. 
M. barbata, Zamark, Anim. sans vert., ii., p. 178; M. cereoides, 
Gray, Dief. N.Z., i, p. 293, nec Cellaria cereoides, Ellis. Cells 
immersed, the mouth only projecting ; surface granulated ; mouth not 
thickened ; a long bristle on each side of the mouth; white or pale 
brown ; in time the bristles fall off, but their position can always be 
recognized by a cup-shaped depression. 
Lyall Bay. Cape of Good Hope. 
The only species of the genus. 
FAMILY—IDMONEIDz. 
Zoarium erect, simple or branched ; branches continuous, cylindrical 
or sub-compressed, free or anastomosing. 
Genus, IDMONEA—Lamouroux. 
Zoarium ramose, branches dichotomous or irregularly divided; free 
or anastomosing ; mouths of cells disposed in parallel, transverse or 
oblique, usually alternate, rows on each side of the front of the 
branches, which are angular or carinate in the middle. 
I. giebeliana, Sto/iczka, Reise d. Novara, Pale., p. 115, pl. xviii., f. 
4-6. Dichotomous, branches depressed, anastomosing ; cells irregular, 
sometimes single, sometimes in series of three or four, and sometimes in 
clusters of four to eight ; mouth round, raised ; both surfaces minutely 
punctate ; branches elliptical. 
I. radians, Lamark, Hist. Anim. sans vert., 2nd ed., p. 279; Busk, 
Lc., p. 11, pl. vii., f- 1-4. Zoarium usually procumbent, stipitate, some- 
times sub-erect ; branches, dichotomous, radiating more or less regu- 
larly in a circular form from the centre, very angular in front ; dorsal 
surface, perforated ; cells, one to four in each series, the innermost the 
longest ; aperture (when quite perfect) bi-labiate. . 
New Zealand and Australia. 
Genus, HORNERA—Lamouroux. 
Zoarium ramose ; branches dichotomous and free ; cells opening on 
one side only of the branches, which surface is marked with wavy 
anastomosing ridges, in the more or less rhomboidal interstices of which 
the openings of the cells are situated. 
H. striata, Wc/ne-Edwards; Stolicska, Reise d. Novara, Pale.,p. 107 ; 
pl. xvi., f. 8-11. Zoarium cespitose ; branches cylindrical, not reticu- 
lated ; mouths of cells disposed more or less regularly in longitudinal 
series, small, orbicula, those towards the lower part of the branches with 
