[Puoc. L'OY. Soc. Victoria, 31 (N.S.), Pakt IE., 1919.] 



Akt. XII. — Farther Notes on Australian Hydroids —IV. 



By W. M. bale, F.B.M.S. 



(With Plates XVI. and XVH.). 

 [Read 10th October, 1918]. 



SiLicuLAUiA UNDULATA (M. and T.) 



Eucopella u/tdulata, Mulder and Trebilcock, G^elong Natur- 

 alist (2), vi., 1914, p. 10, pi. ii., figs. 5-7. 

 Sdicidaria imdidata. Bale, Proc. Koy. Soc. Vict., N.S.. 

 xxvii., 1914, p. <S9. 



I liave to thank Mr. K. E. Trebilcock for specimens of thia 

 hydroid, stained and mounted in balsam, which have enabled me 

 to examine the structure more satisfactorily than was possible with 

 my specimens of S. campawdaria, in which the hydranths were 

 partly retracted, and blackened to almost complete opacity. In 

 Mr. Trebilcock's specimens the hydranths were widely expanded,, 

 rendering the investigation of their structure comparatively easy. 



The hydrothecae are similar to those of H. campanidaria, and 

 the lateral inflations of the hydranths are obvious; these, however,, 

 are not in any way to be regarded as distinct structures, the condi- 

 tion simply being that the body is *' lop-sided," the inflated side 

 occupying the space over the lower lip of the hydrotheca, while 

 tlie distal portion of the hydranth leans over the opposite lip. 

 The peduncles are spirally undulated, like those of Orthopyxisr 

 v(dicu]((f(i. and they are gradually enlarged at their junction with 

 the hydrotheca, in marked contrast to those of S. camjxinnlaria^ 

 whicli Iiave their thick walls narrowed in at the corresponding 

 points. It is interesting to note the paralleli?^m in regard to the 

 peduncles of Orthojyyxis and Silieidarid, the massive thick-walled 

 straiglit peduncles of ,S'. campanidaria having their counterparts inr 

 0. comprei^m and 0. anffuhita, while the thin wavy stalks of ^S*. 

 xinduldta coriespond similarly with those of 0. calictdata and 

 other species. 



The point of most interest is the structure of the oral region, 

 especially as this proves identical in its main features with Wiat of 

 Ovthopy.iU callculata, and also with thati of Catajfoufdaria cf rand Ik 

 Allman, the latter of which has been made by Broch the type of a 

 new family — the Bonnkviklmdak. 



