A MONOGRAPH OP THE TERTIARY POLYZOA OP VICTORIA. 103 



Porina, D'Orbigny. 



Zoarium encrusting or erect and uni- or bilaininate or cylindrical. Zooecia with 

 the thyrostome subcireular, the peristome produced and having one or more suboral 

 pores opening into its cavity above the operculum. 



The essential character of this genus is the presence of one or more suboral 

 pores opening into the peristomial chamber in front of the operculum, and so 

 differing from the special pores of the MicroporellidaB, which open into the body 

 cavity. 



1. P. gracilis, Milne Edwards, sp. PI. XIV., figs. 21-24. 



JEschara gracilis, Milne Edwards, Sur les Eschares, p. 28 ; Busk, B.M.O., II., 

 91 ; C.P., Pt. I., 141 ; McG., P.Z.V., 48 ; Cellaria coronata, lleuss, Eoss. Polyp, der 

 Wien. Tert., p. 62; Porina coronata, Waters, Q.J.G.S., 1881, p. 333; Spiroporina 

 vertebralis, Stoliczka, Eoss. Bryoz. der Orakei Bay, p. 106 ; Porina Dieffenbacliiana, 

 id., p. 135 ; Leptobothrus spenceri, T. S. Hall, T.R.S.V., Oct., 1892, described as a 

 Stylasterid. 



Zoarium encrusting, lobed and bilaminate, or cylindrical. Zooecia mostly 

 indistinct in the crustaceous and lobed form, more distinct in the cylindrical, surface 

 closely pitted ; thyrostome circular or wider than high ; peristome thickened and 

 slightly raised, or much elongated and tubular, in both cases with a circle of small, 

 round, frequently elevated avicularia on its free edge ; peristomial pore immediately 

 below the thyrostome or a short distance down the zoarium ; small avicularia similar 

 to those round the thyrostome scattered irregularly over the zoarium, and occasion- 

 ally a few large spatulate ones. 



The following varieties may be indicated, taking the lobed form as the 

 typical : — 



Var. (a) dieffenbacliiana, Stol. Branches cylindrical ; zocecia irregularly 

 arranged. 



Var. (b) vertebralis, Stol. Branches cylindrical ; zooecia arranged verticillately. 



Var. (c) tubulifera. Branches cylindrical, slender ; zocecia with the peristome 

 much produced and tubular. 



S.P. ; M.O. ; B. ; C.B. ; Belm. ; M. ; C.C. (W.) A common living Australian 

 species. 



The lobate form is that usually found recent, while the great majority of the 

 fossil specimens are cylindrical. 



