Australian Hydroids. 131 



■on the stems of tlie pinnate form, except that they are opposite and 

 generally in contact in front. I have seen an alinormal case of a 

 hydrotheca being transformed and continued as a branch. The 

 hydrotheca-bearing portion of the pinna is separated from the 

 dadophore by a sliort internode. exactly as in S. marginata. 



The gonangia are pear-shaped, tapering below, not compressed, 

 but circular in section, and with the outline towards the summit 

 somewhat concave outwardly, thus differing from the " round- 

 shouldered " compressed form found in certain species otherwise 

 Tery closely allied to S. tenuis. 



Sertularia divergens Busk. 



Sertularia divergens, Busk, Voy. of Rattlesn.. i.. 1(S52. p. 



392; Bale, Aust. Hyd. Zooph. 1884, p. 81. pi. v., fig. :5. 



pi. xix., fig. 16; Billard, Ann. Sci. Nat. ser., ix.. 



1909, p. 322. 



Not Bynamena divergens, Lamouroux, Hist. Polyp. Cor. 



Flex., p. 180, pi. v., fig. 2. 

 (?) Not Sertularia moluccana, Pictet, Rev. .Suisse de Z<m.1. 

 i., 1893, p. 50, pi. ii., figs. 42, 43. 

 This species or variety differs from S. tenuis in the more compact 

 liabit, the shorter hydrothecae and internodes, and the closer pinnae, 

 which are somewhat more divergent. The pinnate habit seems more 

 ■confirmed; indeed, I have not yet observed any of the unbrauched 

 shoots which in .S'. tenuis predominate, though such will doubtle.ss 

 occur. 



Pictet considered his S. moluccana a variety of this species, but 

 he renamed it because he regarded it as distinct from Lamouroux" 

 species. I do not think S. moluccana is the same, judging bv 

 Pictet's figure. He mentions that the ramification agrees with my 

 description, but the ramification is common to many other species. 



The investigations of Billard confirm the opinion expressed ])y 

 Pictet, and earlier by myself, that this is not the D. divergens of 

 Lamouroux, but as that species is the same as S. hicuspidata, Lam- 

 :arck, which name Billard has adopted, the name may stand as 

 S. divergens, Busk, unless it be treated, as Billai-d with nnuh 

 reason proposes, as a mere variety of S. tenuis. 



Sektui..\ria acanthostoma Bale. 



.Sertularia acanthostoma. Bale, Jouin. Micr. Soc. Vict., ii., 

 1881, p. 23, pi. xii., fig. 4; id., Aust. Hydr. Zooph., 

 1884, p. 85. pi. iv., fig. 7, 8; Billard. Arch. d. Zool. 



