Australian Hii<lroiih. 1*27 



//„/,._ Williamstown. I'.-rt Pliilli]). 



I liavc ill the iiiain tolli>\v<'(l IJillai-.l in the synonymy of this 

 species, a(l(liii<r, liowevrf. S. lire riri/(itliu-<. and excluding the tAvo 

 unbi-ainlu'd I'oiins. N. locitloxd and .s'. t ttrhi luttn . already treated of. 

 The two hittci- foiins, l)esides l)eing always, so far as is known, 

 unhraiulied. ditfei- from the present in the form of tlie gonangia, 

 whieii ai-e rouiKled in section, with a wide operculum covering the 

 whole of the sunnnit, while those of tlie pinnate form are plano- 

 eonvex, witli twd iiietirved hoins at the uiJi>ei' angles, and opcnin<i 

 by a narrow slit. It haj^pens that the onlv specimens hithei-to 

 recorded with tlie gonosome sufficiently pi-eserved for the sex to be 

 ascertained are those of S. inf.ata, observed by Ritchie, which bore 

 male gonophores, and those of S. Inctdosa, seen by Warren, in which 

 the gonophores were female. Billard thereupon suggests that this 

 may be a case of sexual dimorphism, the pinnate form being habitu- 

 ally associated with tlie male sex. and the iinliranched form with the 

 female. This view is not supported by any direct evidence, nor, 

 so far as I am aware, is any analogous ease known ; I consider, 

 therefo)-e, tliat the pinnate and the simple forms should by no means 

 be united until their affinities are actually pi-oved. It may also be 

 remarked that >'. infafa is not always pinnate, though unbranched 

 forms liave not hithei-to lieen referred to' it : tlie N. hrevicyathus, 

 found by Versluys in the same ilredging with liis .S'. infldta. is 

 almost certainly merely an unbranched foiin of the latter species; 

 and in my own specimens, which agree alisolutely with S. inflata 

 (so far as ean be ascertained in the abst'iue of the gonosome). I 

 find simple and pinnate shoots growing fiom the same hydrorhiza, 

 •or even, in one instance, the stem of a pinnate shoot running otit 

 into a stolon, which, in its turn, gives origin to an unbranched 

 shoot. These simple forms differ from N. lonilosa in the thinner 

 perisarc, the more sharply triangular teeth, and the tendency 

 (which is also exhibited by the piniiate form) foi- the ridge of the 

 hydrotheca to become weaker, or sometimes (|uite obsolete, in the 

 distal portions of the colony. But I doubt Avhether these distinctions 

 are constant, and should not regard them as of specific value if 

 the gonosome proved to be similar in each case. 



S. hrevicyafhua is not distinguished from S. iii-flafa except l)y the 

 simple habit, and liy points of structure known to \m- varial)le in the 

 species of this gi-ouj), siu-h as the jiresence of a third tooth on the 

 border of the hydrotheca. 



Ritchie agrees with Congdon that the operculum of iS'. itiflafn has 

 a large abcauline and two smaller latero-adiauline valves, but feels 



