12 
THE VOYAGE OF H.M.S. CHALLENGER. 
the exserted portion being of a very thin and delicate texture rarely shows the orifice 
in a perfect condition. It may perhaps be identical with M. d’Orbigny’s Idmonea 
canariensis (Palseont. Frany , p. 732) ; but as neither figure nor sufficient description of 
that species are given, and it is merely stated to be “ slender as a thread and almost 
round, with very few cells,” it is impossible to be certain. 
(4) Idmonea australis, Macgillivray (PI. III. fig. 3). 
Idmonea australis, Macgilliv., loc. cit., Dec. vii. p. 30, pi. lxviii. fig. 2. 
Character. — Zoarium of small size (| to § inch), irregularly branched once, each 
short branch terminating in a single fork ; branches contorted and sometimes twisted ; 
four to six zocecia in each series, the inner the longest ; no intermediate longitudinal 
space in front between the series. Zocecia very slender (0T2 mm.), connate below, but 
when perfect much produced or free for one-half or two-thirds of their length, slightly 
tapering, some nearly straight and ascending obliquely, but towards the upper part of 
the branches curved forwards, not flattened in front; series 0‘7 to l - 0 mm. apart. 
Branches compressed, rounded both in front and behind, about 0 - 6 mm. wide, everywhere 
minutely dotted, up to the border of the aperture ; dorsal surface very finely striated 
longitudinally, intermediate spaces with very minute dots in irregular longitudinal series. 
Habitat. — Station 163b, off Port Jackson, 30 to 35 fathoms, rock. Off Marion Island, 
50 to 75 fathoms. 
[Port Philip Heads, 10 to 15 fathoms, Macgilliv.] 
A very distinct and well-marked species, easily recognisable by the compressed form 
of the branches, which on section are oval, as well as by the extremely fine punctation, 
or rather white dotting of the surface, and the fine or close longitudinal striation of the 
dorsal aspect. It appears to vary very much in the length of the exserted portion of the 
zocecia, which, in the specimens from Marion Island, forms more than half the length of 
the cell (PL III. fig. 3). The exserted part is very slightly tapering and no part of it 
appears to be peristomal, as the wall exhibits the minute punctation quite up to the 
orifice, and there is very rarely any appearance of annular lines of growth. None of the 
specimens present any ocecial chamber. 
Mr. Macgillivray suggests that this species may prove to be a form of Idmonea 
atlantica, but for this view I can see no grounds whatever. 
(5) Idmonea eboracensis, n. sp. (PI. III. fig. 4). 
Character. — Zoarium very small, not more than ^ inch high; branches very short 
and irregular, once furcate, much compressed, 0’6 mm. wide ; dorsal aspect rounded, longi- 
tudinally striated but not grooved. Striae (fig. 4c), about O'Ol mm. apart, a single irregular 
