HYDROZOA RITCHIE. 847 



' hydrorhizal tubes are subjected to unusual buffeting and rough 



• usage owing to wave action or other causes. 



Gonosome. — Gonangia are present on several of the colonies. 



Dimensions. — 



Total height up to 9 mm. 



Stem internode, length 0-45-0-53 mm. 



,, ,, diameter at base of hydiotheca 0'15 mm. 



Hydrotheca,^" length of external profile 031 ,, 



,, length of free portion 17-0-20 mm. 



,, ,, of adnate portion 0-25-0'28 ,, 



,, diameter at mouth 007-009 ,, 



• Gonangium, length 1'09-1-15 ,, 



,, maximum diameter 0'75-0'82 ,, 



Localities. — Station 34, off Port Jackson, three and a half to 

 two and a half miles from shore ; depth, 39 to 36 fathoms ; 

 bottom, sand and mud; 10th March, 1898; not common, growing 

 on a Polyzoon. Station 36, off Botany Bay, one mile from shore ; 

 depth, 23 to 20 fathoms; bottom, sand to rock; 11th March, 

 1898; in clusters on foreign objects. 



SYKTHECIUM CYLINDRICUM {Bale). 



Sertularella cylindrica, Bale, Proc. Linn. Soc. N. S. Wales, (2), 

 iii., 1888, p. 765, pi. xvi., fig. 7. 

 Var. — Sertularella cylindrica, var. pusilla, Ritchie, Proc. Zool. 

 Soc, 1910, p. 817, pi. Ixvii., fig. 9. 



Sertularella halecina, Torrey, Univ. California Publ., Zool., i., 

 1902, p. 61, pi. v., fig. 55, pi. vi., fig. 56. 



Synthecium cqlindricurn, Nutting, American Hydroids, Pt. ii,, 

 1904, p. 136, pi. xli., fig. 7. 



Stations 44 and 48. 



The occurrence of many colonies in this collection allows of 

 the addition of several details, especially as regards variation, to 

 the description of Bale, and to my recent notes on diminutive 

 Indian Ocean specimens. Most striking, on first examination, is 

 the evil condition of the colonies, for the hydrotheese, having 

 extremely tliin walls, have almost all collapsed, and many have 

 been wrenched from their places. 



Trophosome. — A creeping hydrorhizal tube ramifies over a 

 branched Isid Alcyonarian, and anastomoses with neighbouring 

 tubes, thus forming an entangled mesh-work. From this, afc 



3'' Measurements taken to tip of teeth. 



