198 HYDROIDS FROM NEW SOUTH WALES, 



the case of Sertularella adpressa Ritchie* and Thecocladium flahel- 

 lum Allmanf. The insignificant stalk of the gonangium arises from 

 the side of the stem or branch opposite the base of a hydrotheca. 

 The gonangia are large and ovate, with a short tubular neck with 

 a slightly everted lip, and three short apical teeth. They are sur- 

 rounded by eight annular ridges, except on the back where the 

 longitudinal furrow, into which the annulations do not extend, is 

 appressed to the branch. The lower proximal portion is smooth, or 

 with very faint traces of annulation. The extreme distal portion 

 of the gonangium j^rojects forward, and has the ridges completely 

 annular. The gonangia average 1-8 mm. to 21 mm. in length, by 

 0-70 mm. to 0-80 mm. in maximum diameter. The aperture has 

 an internal diameter of 0-20 mm. to 0-24 mm., with a slightly 

 everted lip 0-26 mm. to 0-31 mm. across. 



Dimensions. 



Internode, length 0*75-0'94 mm. 



Interiiode, diameter ... ... ... ... ... 0"22-0*29mm. 



Hydrotheca, length adnate ... ... ... ... 0"57-066mni. 



Hydrotheca, length free ... .. ... ... 038-0"43mm. 



Hydrotheca, diameter at mouth ... ... ... 028-0 32 mm. 



Gonangium, length ... .. ., ... ... l*80-2'10mm. 



Gonangium, maximum diameter ... ... ... 0"70-0'80mm. 



As the above measurements show, there is some variation in the 

 proportion of the adnate part of the hydrotheca, but the propor- 

 tion is generally over a half, and frequently as much as two-thirds 

 may be adnate. 



In his Report on the Hydrozoa of the "Thetis" Expedition, 

 Ritchie has described several specimens as a variety of Sertularella 

 longitheca Bale, although "none of the characteristic gonangia 

 were present, but in spite of this, and of the divergences from 

 typical specimens. . . . I do not hesitate to regard these as belong- 



* Ritchie, Mem. Austr. Mus., iv., 16, 1911, p.838. 

 fAllman, Rep. Sci. Results "Challenger" Exped., Zool., 

 Hydroida, Ft. ii., 1888, p.81. 



