on the Polyzoa. 163 



described the opesia is to a considerable extent concealed 

 when the front wall is removed, and is represented by a large 

 foramen on each side of the calcareous plate, supporting the 

 orifice ; whereas in 8. magnilabris both opesia and the cavitj 

 of tlie cell below it lie open *. 



These differences in the cell arc connected with important 

 differences in the ooecial arrangements. In S. magnilabris 

 there is no external ovicell, but its place is probably filled 

 by a large internal chamber. The section to which -S*. Rozieri 

 belongs is remarkable for the size of its bilobate ooecia, closed 

 in front by a movable lid. For the section of the Steganopo- 

 rellidge represented by Memhr. antiqua^ Busk, Dr. Jul- 

 lien's name Bmittipora may be adopted, but with a wider 

 application than he has given to it. The differences between 

 this germs and his Onychocella are, in my judgment, of 

 slight importance, and the two groups, which agree in all 

 essential characters, may be united under one name. 



For the magnilahris section, Smitt's Steganoporella will be 

 the proper designation. For the Rozieri division I propose 

 the name TJialamoporeUa. The development of the cell in 

 this genus can be well traced at the growing extremities of the 

 branches in an erect and cylindrical form of T. Rozieri^ form 

 gothica^ which I have received from California. In the 

 earliest stage the zooecium is a simple oblong box of consider- 

 able depth, closed in above by a delicate and transparent 

 membrane. There is no sign whatever of the oral valve, nor 

 any trace of the internal lamina. In a more advanced stage 

 an arch of rather deeper horn-colour than the surrounding 

 membrane makes its appearance at the top of the front wall ; 

 this gradually becomes more pronounced, and at last the lower 

 margin, completing the oral semicircle, is faintly outlined 

 below it. In adult cells the margin round the orifice becomes 

 thicker, and is slightly produced at the articular angles. 



The operculum resembles in structure that of the Mem- 

 braniporidan genus Thairopora, MacG. In the younger zooecia 

 there is no trace of any internal structure ; the growth of the 

 lamina commences later on at the lower extremity of the cell. 



Besides the forms already mentioned, the Caleschara of 

 MacGillivray f belongs to the Steganoporellidse.. Avicularia 

 seem to be wanting, and it is furnished with ocecia of the 

 ordinary type. It is nearly allied to Smittipora, if not a 

 member of that genus. 



Another species which must be referred to this family is the 



* I hope to give figures illustrating the structural differences in a future 

 paper. 



t ' Zoology of Victoria/ dec. v. p. 45. 



