19. 



20. 



21. 



22. 



BRITISH MARINE GENERA 527 



Characters as in No. 6 . Eucmtea chelata, Huxleya fragilis 



Zooecia biserial. Aperture large, the semicircular orifice at its upper 

 end, where there is commonly a short spine Cellularia peachii 

 Zooecia in one or two series. Branches originating from the backs 

 of the zooecia, and facing in the opposite direction to the parent 

 branch. Aperture small . . . Scruparia clavata 



One or more conspicuously long marginal spines. Avicularia present 

 or absent ...... Bicellaria 



Zooecia uniserial (see No. 5) . . . . Brettia 



Zooecia biserial, in short internodes. An inconspicuous avicularium 

 below the aperture. Fornix present . Menipea jeffreytii 



Colony consisting of a network of narrow branches, the zooecia 

 opening only on one of their surfaces . . Eetepora 



Colony large, brittle, composed of contorted plates, uniting irregularly, 

 usually composed of two layers of zooecia. Orifice large, indented 

 laterally ..... Lepralia foliacea 



Branches delicate, cylindrical . .22 



Branches or lobes coarser, not necessarily cylindrical . - 24 



Branches composed of four rows of zooecia . .23 



Zooecia in more than four regular, longitudinal rows. Peristome 

 raised, and, with the ovicell, forming a swelling on the surface of 

 the branch . . . Escliaroides quincuncialis 



(Orifice circular. A row of pores round the margin of the zooecium. 

 A median pore resembling a small orifice below the true orifice. 

 Small lateral avicularia . . Porina borealis 



I Orifice surrounded by a peristome, produced into a mucro beneath 

 [ the orifice. No pores . . . Palmicellaria elegant 



( Zooecia arranged in regular series . . . .25 



I Zooecia irregularly heaped, their long axes often perpendicular to 

 I the surface of the colony. Mucro largely developed, concealing 

 ' the form of the orifice, and bearing an avicularium Cellcpora 



( Orifice with a sinus ; or peristome interrupted or extended below 



I into a sinus-like outgrowth, which usually includes a small 



' I avicularium . .26 



I Neither median sinus nor interrupted or extended peristome . 28 



/ Orifice with a sinus . . . Schizoporella (Fig. 239, B) 



\ Peristome interrupted or extended below . . .27 



Branches of various forms. Surface of the older parts very even. 

 Secondary orifice rather long, usually wider above, enclosing a 

 small avicularium below, and appearing as a hole in the even 

 surface of the branch . . Porella (Fig. 255, B, C) 



27. 



A prominent tooth projects into the orifice from its lower side. 

 Zooecia with thin walls . Smittui landsborovii (Fig. 239, C) 



No tooth in the orifice, at the side of which is a small avicularium 

 Old zooecia with thick walls. Colony composed of a short stem 

 and flattened branches . . . Escharoides rcsacea 



