416 THE AUSTRALIAN HYDROMEDUS.E, 



DIPHASIA MUTULATA. Bale. 



This species found in Prince of Wales Channel and described by 

 Busk (1) has also been placed among the Diphasia by Bale (2.) 



DIPHASIA SUB-CARINATA. Bale. 



This species found in Bass' Straits and in many parts of 

 Australia, and described by Busk (3), has been placed among the 

 Diphasia by Bale (4.) 



4. GENUS. SERTULARELLA. Gray. 



Branching colonies. Trophosomes biserial and alternate, with 

 an Operculum composed of several pieces of chitin. The Gonothecse 

 are usually ringed transversely. 



The structure of Sertularella Polyzonios has been investigated 

 by Weismann. 



SERTULARELLA MICROGONA. Nov. sp. 

 Plate VII., fig. 1-3. 



From a creeping Hydrorhiza, stems about 1 cm. in height ai'ise, 

 which bear the distant Trophosomes, and the exceedingly small 

 Gonosomes. The Trophosomes are wide at the base and narrower 

 at the mouth which has a toothed circumference because there are 

 4 bites in it, as it where which leave four protruding teeth between 

 them. The Gonangium is oval and compressed. It has no 

 evident rings on its surface, the Polypostyl is a cylindrical body, 

 thickest in the middle which appears connected with the inner 

 surface of the Gontheca by many cellular strings. 



I found this Hydroid in Port Phillip (Victoria) on stones in the 

 Laminarian Zone. 



(1.) Busk. Voyage of H. AI. S. Rattlesnake, p. 391. 



(2.) Bale. Catalogue of the Australian Hydroid Zoophytes, p. 101. 



(3 ) Bask.. Voyage of H. M. S. Rattlesnake, p. 390. 



(4.) Bale. Catalogue of the Australian Hydroid Zoophytes, p. 102. 



