Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to
Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to
Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to
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174<br />
hydro<strong>the</strong>ca. No such patches were found in D.<br />
disticha. However, not enough well preserved<br />
material could be examined <strong>to</strong> substantiate this<br />
difference.<br />
Both D. moluccana and D. disticha have a<br />
very thin and delicate hydro<strong>the</strong>cal perisarc. It is<br />
<strong>of</strong>ten damaged or dis<strong>to</strong>rted in preserved samples.<br />
Toge<strong>the</strong>r with <strong>the</strong> frequent renovations <strong>the</strong>y can<br />
look deceptively like hydro<strong>the</strong>cae <strong>of</strong> <strong>the</strong> genus<br />
Salacia. A careful search for undamaged hydro<strong>the</strong>cae<br />
will, however, reveal <strong>the</strong> difference (cf.<br />
Medel & Vervoort 1998: 31 and Cornelius 1979:<br />
309, note 21). The flimsy perisarc is actually an<br />
important trait <strong>to</strong> distinguish D. disticha from D.<br />
pumila. A fur<strong>the</strong>r difference is <strong>the</strong> separation <strong>of</strong><br />
<strong>the</strong> hydro<strong>the</strong>cae: <strong>the</strong>y are not contiguous on ei<strong>the</strong>r<br />
side. Dynamena pumila also forms branched<br />
and unbranched forms (see Cornelius 1995b<br />
or Schuchert 2001 for recent descriptions).<br />
Dynamena pumila occurs in cooler waters <strong>of</strong> <strong>the</strong><br />
North Atlantic, while D. disticha is predominantly<br />
known from warmer water.<br />
The material identified by Pictet (1893) as<br />
Sertularia gracilis Hassal, 1848 (MHNG INVE<br />
25032) is clearly a Dynamena species and resembles<br />
somewhat D. moluccana, although it has<br />
simple shoots. But <strong>the</strong> hydro<strong>the</strong>cae are distinctly<br />
smaller (0.2 mm abcauline side) and <strong>the</strong>y are on<br />
long internodes. It could thus belong <strong>to</strong> Dynamena<br />
dalmasi (Versluys, 1899) (see Calder 1991<br />
and Medel & Vervoort 1998 for recent descriptions).<br />
Distribution<br />
Indonesia (Pictet 1893, Billard 1925b), Papua<br />
New Guinea (Thornely 1904), Marshall Islands<br />
(Cooke 1975), Australia (Bale 1884, as S. divergens),<br />
Seychelles (Jarvis 1922 as S. cornicina<br />
var. pinnata), sou<strong>the</strong>rn Africa (Millard 1975),<br />
Japan (Hirohi<strong>to</strong> 1995, as D. exigua). Type locality:<br />
Bay <strong>of</strong> Ambon.<br />
Geminella ceramensis (Billard, 1925)<br />
Fig. 31.<br />
Sertularella ceramensis Billard, 1925a: 649. – Billard<br />
1925b: 170, fig. 30, pl. 7: fig. 20.<br />
Geminella ceramensis. – Vervoort 1993: 109, fig. 3a–e.<br />
Not Geminella ceramensis. – Vannucci Mendes 1946: 570,<br />
pl. 4: figs 40–41.<br />
P. SCHUCHERT<br />
Fig. 31. Geminella ceramensis (Billard, 1925). A. Pair <strong>of</strong><br />
hydro<strong>the</strong>cae. B. Hydro<strong>the</strong>cal opening in oblique view showing<br />
<strong>the</strong> three opercular valves. C. Gono<strong>the</strong>ca. – Scales: A–B<br />
= 0.1 mm; C = 0.2 mm.<br />
Material examined:<br />
Kei Islands Expedition station 57, with gono<strong>the</strong>cae.<br />
Description<br />
Colonies erect, stems irregularly branched, up <strong>to</strong><br />
1 cm in height. S<strong>to</strong>lons tubular, ramified. Stem<br />
and branches with identical structure, regularly<br />
segmented by more or less distinct transverse<br />
nodes. Segments elongate, 0.7–1.1 mm long,<br />
each with a pair <strong>of</strong> opposite <strong>to</strong> subopposite hydro<strong>the</strong>cae<br />
in its middle. Side-branches originate<br />
below a hydro<strong>the</strong>ca, first segment without hydro<strong>the</strong>ca,<br />
about half as long as o<strong>the</strong>r segments.<br />
Hydro<strong>the</strong>ca conical, adcauline side adnate<br />
for half or less <strong>of</strong> length, abcauline side almost