Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

176
branched, unsegmented or only few nodes
present, bearing a double row of alternate, overlapping
hydrothecae on the frontal face, the two
rows contiguous with one another.
Hydrotheca tubular, basal half parallel to hydrocladium,
distal half curving away, length of
abcauline side 0.6 mm, no internal teeth, rim with
two indistinct lateral teeth, operculum composed
of an adcauline flap, the base of which is not
distinctly demarcated from hydrotheca, margin
of hydrotheca often renovated and elongated like
duck-bill.
Gonothecae on stem, urn-shaped, 1.6 mm
long, diameter 0.8 mm, with 8–10 longitudinal
ridges, these partly serrated, distal aperture on
conical collar.
Remarks
The alternate hydrothecae on the anterior surface
of the hydrocladia, as well as the characteristic
hydrothecae, make this species easy to identify.
However, it is arguable why this species should
be placed in a separate genus Idiellana and not in
the genus Diphasia. The only difference between
the two genera is the alternate arrangement of
the hydrothecae in Idiellana. Hydrothecae on
one side of the hydrocladium are also frequently
found in Diphasia species.
Distribution
Widely distributed in tropical and subtropical
regions of the world. Type locality: Australasia
(as New Holland in Lamouroux, 1816).
Salacia hexodon (Busk, 1852)
Fig. 33.
Pasythea hexodon Busk, 1852: 395. – Bale 1884: 113, pl. 9:
fig. 13. – Bale 1888: 771, pl. 14: figs 8–9. – von Campenhausen
1896b: 311. – Watson 2000: 21, fig. 16A–B.
Salacia hexodon. – Billard 1925b: 207, fig. 49C–D.
Material examined:
Kei Islands Expedition stations: 15. – 18. – 20. – 60. – 61. –
67. – 68. – 71, with gonothecae. – 72, with gonothecae. – 90.
– 107.
Description
Colonies erect, simple or irregularly branched,
0.5–2 cm high, monosiphonic, with regular
P. SCHUCHERT
Fig. 33. Salacia hexodon (Busk, 1852); station 71. Part
of shoot showing typically clustered hydrothecae, a sidebranch,
and a gonotheca. – Scale: 0.5 mm.
transverse nodes above groups of hydrothecae.
Hydrothecae on lateral sides, clustered in groups
of 5–7 (range 2–10, reportedly also more), within
these clusters consecutive individuals of one row
in contact, the two rows not contiguous, long,
tubular regions between the groups of hydrothecae.
Branching points of side-branches below
a hydrotheca.
Hydrotheca tubular, abcauline side 0.4 mm,
curved, adnate for half of its adcauline length,
opening circular, angle variable, opening-plane
parallel to stem or inclined towards below, with
single operculum attached to abcauline side. Hydranth
without abcauline caecum, one abcauline
tentacle longer than others, thick club-shaped
with larger nematocysts than in other tentacles.
Gonothecae arising below lowest hydrotheca