HYDROIDA. BALE. 271 



Fuller investigation will be necessary to determine the 

 true function of the apertures or receptacles described above, 

 also to ascertain whether they are sufficiently constant to 

 be of service in the discrimination of species or varieties. 

 In my specimens of S. muelleri they are fairly frequent, but 

 though the circular smooth-edged orifices are distinct enough 

 I failed to find any trace of tubes surrounding them ; indeed 

 they often have, in this species, the appearance of being 

 closed in by an excessively thin pellicle of perisarc. It is 

 just possible that they may correspond to the minute conical 

 protuberances found on the apophyses of many Piumularians, 

 the function of which is doubtful. 



S. furcafa, Trask, is evidently very closely allied to *S'. 

 minima, and judging from some of the published figures of 

 the former it seems possible that the two species may 

 ultimately have to be united. 



Billard, who has examined the type of S. crinoidea, Allman, 

 is of opinion that it is not specifically distinct from aS*. minimu. 



Loc. — Nuyts Archipelago, Great Australian Bight, 10 

 fathoms. 



Sertularia pusilla, nom. nov. 



(Plate xlvi., figs. 3-6.) 



Sertularia minima, Thompson, var. tubatheca, Mulder and 

 Trebilcock, Geelong Nat., (2), vi., 1914, p. 40, 

 pi. iv., fig. 1-ld. 



Not Sertularia tubitheca, Allman, Mem. Mus. Comp. Zool. 

 Harvard, v., 1877, p. 24, pi. xvi., figs. 5-6. 



Shoots about 6-8 mm. in height, unbranched, sometimes 

 divided into regular internodes, each bearing one pair of 

 hydrothecse, but often with nodes indistinct or quite wanting 

 on parts of the hydrocaulus or throughout. 



Hydrothecse in pairs, opposite, tubular, regularly curved, 

 mostly in contact in front, separate behind, moderately 

 divergent ; aperture looking outward and upward, with two 

 pointed angular lateral lobes. 



Minute tubular sarcothecae (?) on the lower portions of some 

 of the internodes. 



Gonothecse one on a shoot, borne by the proximal inter- 

 node ; somewhat compressed, ovate or oblong, with the 

 shoulders rounded, and a distinct collar, very slightly 

 elevated, with minute internal denticles. 



