Australian Hydro ids. 337 



Sektulakklla rentoni Bartlett. (Plate XVI., Fig. 2). 



Sertidartlla rentoiii, Bartlett, Geel. Nat. (2), iii., 1907, p. 

 43, tig. — . Mulder and Trebilcock, Geel. Nat. (2), 

 vi., 19U, p. 9, pi. i., %., 4, pi. iii., fig. 1. 



Hydrocaulus simple or pinnate, twisted at the base, about 6 mm. 

 in height, divided by slender twisted joints into internodes, each 

 bearing a hydrotheca about the middle or slightly above. 



Hydrothecae tubular or sub-conical, adnata a little less than 

 half their length, widely divergent and nearly in one plane, aper- 

 ture not contracted, margin with three teeth, one superior and two 

 lateral; no internal teeth. 



Gonothecae springing from the base of the hydrocaulus, large, 

 sub-globular, smooth; a short conical neck rising from within a 

 slight depression at the summit, ajDerture small, entire. 



Loc. — Queenscliff; Bream Creek; (Bartlett). 



The trophosome of this species so closely resembles that of S. 

 pygmaea that it would be no easy matter to distinguish between 

 them with certainty in the absence of the gonangia, w^hich, how- 

 ever, are entirely unlike, those of S. yygmaea being of the annu- 

 lated type characteristic of *S'. Johnston i. The hydrothecae of the 

 present species seem to average slightly longer than those of S. 

 pygmaea, in other respects, including the presence in many cases 

 of a membranous oblique septum, they are alike, as are the angular 

 strongh' twisted internodes. 



S. unilateralis (Lamouroux)i is like iS', rentoni in the gonangia 

 as well as in the trophosome, and seems to be distinguishable mainly 

 by the presence of internal teeth in the hydrotheca. 



Sertularella DiAPiiANA Allinan. (Plate XVI., Fiof. 5). 



ISertularia tridentatay Lamouroux, Hist. Polyp. Cor. Flex., 



1816, p. 187. 

 Thai-aria diayhana (Busk. M.S.), Allman, Journ. Linn. 



Soc-. Zool., xix., 1885, p. 145, pi. xviii., figs. 1-3. 

 Thuiaria hyalina, AUmnn, " Challenger " Hydroida, Pt. 



II., 1888, p. 69, pi. xxxiii., figs. 2-2a. 

 Sertidartlla lata. Nutting, Amer. Sert., 1904, p. 85, pi. 



xviii., fig. 10; Idem, Bull, U.S. Fish Comm., 1905, 



p. 948. Billard, Arch, de Zool. exp. et gen. (4), vii., 



1907, p. 346, fig. 4. 



1 r>illar<I, Aim. Sci. Nat (;)), ix., 1!K)0, i>. Sl.'S, figs. 3, 4. 



