HYDKOIDH OF EASTERN CANADA 



173 



Sertularella polyzonim (Liunteus). 



Trophosome. Stem slender; branching irregularly 

 tilternate; hydrothecae alternate, rather distinct, large, 

 tapering but slightly, the distal half or more, free; 

 margin with four teeth; operculum of four flaps. 



Gonosome. Gonangia large, oval; margin with 

 four stout spines or teeth; surface strongly and regu- 

 larly rugose. 



No. 87. 

 Sertularella polyzonias. 



SrHularella nif/osa (Lmiuh'us). 



Trophosome. Colony small, stem usually un- 

 branched, constricted at regular intervals; h.vdrothecae 

 alternate, rather distinct, fusiform, distinctly rugose; 

 margin with four tentacles ; operculum with four flaps. 



Gonosome. Gonangia oval, rugose; margin with 

 four teeth. 



Serhilarella tricuspidata (Alder). 



Trophosome. Stem slender, lax, branching irregu- 

 larly alternate or dichotomous; hydrothecae alternate, 

 very slightly immersed, tubular, sometimes curved; 

 margin with three teeth; operculum with three flaps. 



Gonosome. Gonangia oval, with strongly crested 

 rugosities; a small, smooth tubular neck bears the aper- 

 ture. 



No. ss. 



Sn-tnlarella rur/osa. 



No. 89. 

 Hertularella tricuspidata. 



Genus Sertularia. 



Trophosome. Hydrothecae in two rows, occurring in pairs, which are strictly 

 opposite throughout, or at least on the distal portion of the branches. 



Gonosome. Gonangia oval or ovate. 



KEY TO SPECIES. 



a Stem with opposite branches, the two hydrothecae of a pair not in contact. 



S. pumila. 

 Stem unbranched, the two hydrothecie of a pair in contact. S. cornicina. 



