764 SOME NEW AND RARE HYDROIDA IN THE AUSTRALIAN MUSEUM, 

 SeRTULARELLA VARIABILIS, ll.Sp. 



(Plate XV., figs. 5-9). 



Hvdrocaulus simple or pinuate, phinse when present alternate, 

 given off just below each hydrotheca on the stem ; stem and 

 pinnte divided by twisted joints into internodes, each bearing a 

 hydrotheca on its upper part. Hydrothecae adnate from J to ^ 

 their height, divergent, both series directed towards the front or all 

 nearly in the same plane, with several more or less distinct trans- 

 verse rugse, contracted near the aperture and swollen below ; 

 aperture with three marginal teeth, one superior and two lateral, 

 also with three internal compressed vertical teeth alternate with 

 those of the margin, or sometimes with three teeth within the 

 lowest side and one within each of the other two sides. 



Gonothecae ovate, with ti'ansverse undulations which vary greatly 

 in number and distinctness, and are often absent from the proximal 

 pai-t ; summit tubular, with from two to six teeth, and a small 

 circular aperture. 



Hah. — Bondi ; Coogee. 



With some hesitation, I include under the name of S. variabilis 

 a series of forms allied to (and partly intermediate between) the 

 -V. indivlsa and S. solidula of the southern coast. The form which 

 may be regarded as the ty[)e difters from «S'. indivisa mainly in 

 having the internodes and hydrothecfe stouter and comparatively 

 shorter, so that for the most part each hydrotheca is nearly or 

 quite in contact with the lower part of the next internode above, 

 while in <S. indivisa the interrodes are slender and elongated, with 

 the joints consisting usually of double oblique constrictions, so 

 that the hydrothecae are more widely separated. The hydrothecae 

 in the present form are also larger, and both series are commonly, 

 but not invariably, directed towards the front, instead of lying in 

 the same plane. The other principal tyjie rejtresentrd in the 

 collection seems more apt to assume the pinnate form, and would 

 not be suspected of any very close affinity with the first variety 

 if it were not for the occui-rence of intermediate forms. The 



