Further Notes on Australian Hydro ids. 101 



occupies a distinct internode, while in Sertularia there are one or 

 more pairs on an internode, and in Thuiaria two series whicli 

 are not paired. A great many species of Sertularella have been 

 described by different authorS, and the essential character men- 

 tioned above seems to be common to all of them, except in the 

 case of two which were described by Professor Allman in his 

 paper on Australian, Cape, and other Hydroida, in the Journal 

 of the Linnean Society for 1885. One of these — S. diffusa — 

 seems to be a true Sertularia, with two pairs of alternate 

 hydrothecse on each internode ; the other — vS. trochocarpa — 

 undoubtedly exhibits strong affinities with S. Johnsioni and 

 similar species, especially in the form of the gonangia, while at 

 the same time the arrangement of the sub-alternate hydrothecse 

 (a pair on each internode) would require it to be placed in the 

 genus Sertularia, an affinity indicated also by the form of the 

 hydrotheca-margin. It may therefore be regarded as a transi- 

 tional form of that genus. 



Sertularella longitheca, Bale. 

 (Plate IV., figs. 7-9.) 



Gonotheca3 with three longitudinal angles, one dorsal and two 

 lateral, the latter more acute and prolonged upwards into two large 

 erect conical hollow processes, dorsal angle sometimes having a 

 similar conical summit, but often terminating in a slight shoulder 

 about the level of the aperture ; summit of the gonangium 

 forming a broad truncated cone between the processes, with a 

 depression at the top from which rises a small conical neck, with 

 narrow aperture. 



Port Phillip Bay (Mr. J. B. Wilson). 



The form of the gonotheca was previously somewhat doubtful, 

 as I had only a single distorted specimen. When the dorsal 

 angle is not prolonged upward the gonotheca in front view is not 

 unlike those of Sertularia elotigata, except in the elevated and 

 narrow aperture. There are no transverse undulations, but the 

 gonotheca is covered with delicate wavy transverse sti'ia?, which 

 appear to be minute ridges. 



The largest specimen is about four inches long, with five or six 

 distant ascending branches. 



