Review of the genus Monotheca (Hydrozoa: Leptolida) from Australia with description of a new species and a note on 
Monothecella Stechow, 1923 
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Figure 2. A-G, Monotheca flexuosa. A, part of stem; B, hydrocladium, lateral view; C, hydrocladium, ventral view; D, male and female 
gonothecae on same stem; E, median inferior nematotheca; F, cauline nematotheca; G, one of twin lateral nematothecae. Scale bar: A, D, 0.5 mm; 
B,C, 0.2 mm; E-G, 0.1 mm. 
Description. Hydrorhiza of thin tubular stolons reptant on 
invertebrate substrate, sometimes intersecting in tangled knots, on 
algal substrate stolons often flattened with flexion joints. Caulus 
of same diameter as stolon, monosiphonic, flexuous, variable in 
length, up to 20 mm, base of stem smooth with a few irregular 
transverse joints; short stems unbranched, some longer stems with 
one or two orders of short side branches, stem intemodes long. 
Hydrocladia alternate, in one plane, borne on a strong 
apophysis below cauline node, apophysis curving smoothly 
away from internode, distal node transverse with rounded 
shoulder. Hydrocladial athecate internode long, cylindrical, 
straight to slightly curved, walls smooth, increasing slightly in 
diameter distally; distal node transverse, deep, a transverse 
septum behind node, typically several transverse internal septa 
in intemode. 
Hydrothecate intemode about same length as athecate 
intemode, almost entirely occupied by hydrotheca, proximal 
node narrow, deep, inserted into shoulder of athecate intemode; 
intemode slightly distally inflated, terminating behind margin of 
hydrotheca, a faint intranodal septum sometimes in intemode 
below hydrotheca. Hydrotheca cup shaped, adcauline wall 
convex, set deeply into internode, abcauline wall weakly 
concave, margin circular, transverse to hydrothecal axis, rim 
delicate, a slight thickening below margin. 
