Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

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186 12a–b. – Stechow & Müller 1923: 471. – Billard 1925b: 150, fig. 19. – Vervoort 1941: 214, fig. 5. – Mammen 1965: 38, fig. 70. – Watson 2000: 28, fig. 23. Sertularella timorensis Billard, 1919b: 21, fig. 1f–g. Sertularella polyzonias var. cornuta Ritchie, 1909: 525. – Ritchie 1910a: 10, pl. 4: fig. 2. P. SCHUCHERT Fig. 41. Sertularella quadridens (Bale, 1884); A–E, typical form, station 18; F–G, variant form “cornuta”, Samalon Island; H– I, variant form “timorensis”, station 26. A. Colony silhouette. B. Stem internode with base of hydrocladium. C–H. Hydrocladial hydrothecae, note variation of spacing and process at end of adcauline side, all drawn to same scale. I. Gonotheca, same scale as B. – Scales: A = 1 cm; B & I = 0.5 mm; C–H = 0.2 mm. Sertularella cornuta. – Stechow 1923: 12. – Nutting 1927: 215, pl. 42: figs 1–2. Sertularella quadridens var. cornuta. – Billard 1925b: 151, pl. 7: fig. 9. – Vervoort 1941: 216. Sertularella quadridens var. timorensis. – Billard 1925b: 153, fig. 20, pl. 7: figs 10–11.
HYDROIDS OF THE DANISH EXPEDITION TO THE KEI ISLANDS Sertularella quadridens forma quadridens Ralph, 1961a: 830, fig. 23h. Sertularella quadridens cornuta. – Vervoort 1993: 232, figs 52b–e, 53a–b. Material examined: Normal form Kei Islands Expedition station 18, several stems, no gonothecae. Morphotype “cornuta” Kei Islands Expedition stations: 16. – 60. – 63. – 64. – 103. – 104. – 106. – Kei Island Expedition, Samalon Island near Ujungpandang, 35 m, 28 Jun 1922. Morphotype “timorensis” Kei Islands Expedition station 26, one shoot with gonotheca, much overgrown by Bryozoa and algae. Description of typical form Colonies erect, pinnate, reaching heights of 7 cm. Stems monosiphonic, unbranched, with alternate hydrocladia which are more or less in one plane, divided into internodes in distal regions only, nodes oblique, sloping alternately to left and right. Each stem internode bearing three hydrothecae in two rows and one hydrocladium, the latter rising just below the most distal hydrotheca. Hydrocladia straight, unbranched, with distant nodes and a variable number of hydrothecae per internode. Hydrothecae alternate, the two rows of hydrothecae on the hydrocladia in one plane, both rows well separated, successive hydrothecae of one row well separated for about somewhat less than the length of one hydrotheca. Hydrotheca tubular, curved outwards, adnate for 2/3 to ¾ of its adcauline length, length of abcauline side 0.30–0.35 mm, diameter of opening 0.20–0.23 mm, length of free adcauline side 0.13–0.18 mm, adcauline side evenly curved, abcauline side straight in lower part and curved in last fourth, opening oblique, margin with four cusps; floor complete, with large pore, lower end of adcauline wall often with an oblique or vertical process, sometimes even connected to opposite hydrotheca (Fig. 41B), size and form of this process very variable within the same shoot (Fig. 41B– D), many hydrothecae even without such a process. Gonothecae of this form not observed (see Watson 2000, Billard 1925b). 187 Variant form “cornuta” Colony 2–5 cm high, hydrothecae slightly larger (abcauline wall 0.35–0.4 mm), hydrotheca more projecting (adnate for 2/3), process at lower end of adcauline wall absent or represented by a slight thickening only (Fig. 41E–G). No gonothecae present. Variant form “timorensis” Colony 3 cm high, perisarc much thickened, a large and massive intrathecal tooth on adcauline side, often also smaller on abcauline side, hydrothecae adnate for 2/3 to ¾ of their adcauline side, length abcauline side 0.38–0.40 mm, diameter of opening 0.15–0.16 mm. Gonotheca on hydrocladia, about 1.2 mm long, diameter 0.5 mm, barrel-shaped, with transverse annulation, end truncate, square, with four sharp corners, operculum pyramidal and composed of four triangular flaps. Remarks Typical Sertularella quadridens have hydrothecae with a characteristic process at the lower end of the adcauline wall (Fig. 41B–D), which renders them relatively easy to identify, even in the absence of the characteristic gonotheca. However, this process is very variable and can be absent in quite a number of hydrothecae. Therefore, also otherwise closely similar colonies lacking this process (variant forms) were here also allocated to this species. One of these variant forms likely corresponds to the form described by Billard (1925b) as S. quadridens var. cornuta. Billard (1925b) distinguished this variant from the typical form through the more widely spaced and more projecting hydrothecae and smaller gonotheca with longer marginal cusps. The status of this variant is at present unclear. Ritchie (1909, 1910a) suggested it to be a variant of S. polyzonias, but Stechow (1923) and Nutting (1927) recognized it as a full species, an opinion also favoured by Watson (2000). Billard (1925b) and Vervoort (1941, 1993) regarded it as a variant of S. quadridens. Another variant is S. quadridens var. timorensis, a morphotype originally described as a separate species by Billard (1919b), but later demoted to a mere variant of S. qua-
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