Review of the genus Monotheca (Hydrozoa: Leptolida) from Australia with description of a new species and a note on 
Monothecella Stechow, 1923 
83 
Monotheca obliqua, measurements (/tm) 
Hydrorhiza, width 
70-88 
Stem 
length of internode 
200-320 
width at distal node 
40-60 
Apophysis 
length of adcauline wall 
26-58 
width at distal shoulder (node) 
40-70 
Hydrocladium 
length of athecate internode 
56-80 
width at distal node 
42-60 
length of thecate internode 
160-104 
Hydrotheca 
length of abcauline wall 
140-200 
length of of adcauline wall 
80-148 
depth, floor to margin tip 
180-200 
width at rim 
160-180 
Nematotheca 
total length of lateral 
52-60 
diameter of cup 
42-48 
length of median 
48-52 
diameter of cup 
26-28 
Gonotheca 
length, including pedicel 
1240-1580 
width at margin 
640-1100 
Remarks. Monotheca obliqua is a well-known species with 
worldwide distribution. Mulder and Trebilcock (1910, 1916) 
briefly described material collected from Bream Creek on the 
Bass Strait coast and Corio Bay in Port Phillip, commenting on 
the slenderness of the base of the median inferior nematotheca, 
the small axillar hydrostatic pore and the abcauline flange 
connecting the base (prehydrothecal chamber) of the hydrotheca 
to the internode. 
Although widely distributed across the south and east of 
the continent, M. obliqua is not a common species in Australia. 
Type locality. British Isles. 
Known distribution. Cosmopolitan; southern Australia to 
Queensland. 
Monotheca pulchella (Bale, 1882) 
Fig. 4 F-L 
Plumularia pulchella Bale, 1882: 30, pi. 15, figs 6, 6a.— Bartlett, 
1907: 43.- Stranks, 1993: 13. - Watson, 1994: 67. 
Not Plumularia pulchella. — Bedot, 1921: 28.— Trebilcock, 1928: 
24. — Totton, 1930: 221, fig. 58 a-d.— Hodgson, 1950: 41, fig. 71.— 
Ralph, 1961b: 39, fig. 5 c-e.- Blanco, 1973: 73, figs 1-3.- Millard, 
1975: 398, fig. 125 C-D.— Izquierdo et al., 1986: 54, fig. 5.— Genzano, 
1990: 50, figs. 16-17.-Medel and Vervoort, 1995: 58, fig. 25.- 
Vervoort and Watson, 2003: 369, 373, fig. 90J-L.— Bouillon, et al., 
2004: 172, fig. 92G-K. 
IPlumularia pulchella — Blackburn, 1942: 108.— Day etal., 1952: 
404.- Millard, 1957: 232.- Millard, 1962: 300.- Pennycuik, 1959: 
180.- Ralph, 1961b: 109.- Millard, 1966: 493.- Berrisford, 1969: 
394.- Day et al., 1970: 14.- Millard, 1978: 196.- Millard, 1980: 
133.— Medel and Lopez-Gonzalez, 1996: 202. 
Monotheca pulchella.— Stechow, 1921: 260.— Watson and 
Mclnnes, 1999: 111. 
Material examined. NMV F59054, Bale collection. Museum Victoria, 
one microslide, labelled in Bale’s handwriting ‘ Plumularia pulchella 
Bale, Queenscliff, November, 1878’. 
Material in author’s collection : microslide and preserved 
material, Knobbies Island, Western Port, on brown alga, coll: J. 
Watson, depth 10 m, 27 Januaryl985. 
Description. Hydrorhiza flat and ribbon-like with flexion 
joints. Stems monosiphonic, straight to weakly sympodial, 
basal athecate region with several transverse nodes often with 
one or two nematothecae, succeeding cauline internodes 
variable in length, cylindrical, robust, nodes deep, transverse to 
oblique, internode typically with several internal septa 
imparting a wrinkled appearance to stem. 
Hydrocladia alternate, usually in one plane, but sometimes 
one or two forwardly displaced, halfway to one-third distance 
up internode, apophysis of stem upwardly directed away from 
internode, long, stout, with a broad transverse distal shoulder, 
usually an internal septum behind shoulder; hydrocladium 
short, athecate internode variable in length, proximal end 
narrow, inserted into shoulder of apophysis. Hydrothecate 
internode variable in length, almost entirely occupied by 
hydrotheca, proximal end of internode a narrow neck inserted 
into athecate node; distal end terminating in a protuberance 
behind hydrothecal margin. 
Hydrotheca cup shaped, adcauline wall convex, immersed 
in internode, abcauline wall weakly concave and thickened; 
margin circular, transverse. 
Nematothecae bithalamic, moveable, cauline and 
hydrocladial median inferior of same size and shape, base long 
and conical, cup deep, rim circular, slightly adcaudally 
shortened; a nematotheca one-third distance up cauline 
internode and two axillar; hydrocladial median inferior seated 
on a prominence of internode, just reaching base of hydrotheca, 
twin laterals seated almost at end of internode, base fairly 
short, cup adcaudally excavated. 
Male and female gonothecae borne on same stem. Sexes of 
same shape, kidney shaped to ovoid, inserted on a smooth, 
short, bent pedicel at base of apophysis, pedicel expanding and 
merging into body of gonotheca; walls of gonotheca thick, 
smooth to faintly rugose, aperture distal, circular, displaced to 
one side, rim slightly thickened, a submarginal row of large, 
irregularly shaped inwardly directed lobate cusps, usually one 
or two larger than the others. Mature female gonophore 
containing a large ovum. 
