528 POLYZOA 



/ A tooth projects from the lower side into the large, subcircular orifice, 



on each side of which is a small oval avicularium (colony erect or 



i encrusting) . . . Mucronella pavonella 



\ No tooth : mucro sometimes present . . . .29 



' Branches cylindrical. Old zooecia with thick walls. Orifice in 

 young zooecia longer than broad ; beneath it a median pore, 

 and in some cases a lateral avicularium with vibraculoid mandible 



Dipomda verrucosa 



^ A distinct mucro, which may bear an avicularium above Palmicellaria 



28. 



29. 



Encrusting Cheilostomata. 



f Usually growing on a small univalve shell. Orifice longer than 



broad, indented laterally. Mucro present . . Lepralia edax 



30. \ One or two conspicuous processes, each bearing an avicularium, near 



the orifice, which is often concealed. Avicularia in many cases 



found on other parts of the colony . . Gellepora 



f Zooecia distant ; or in single rows . . . .32 



' \ Zooecia forming continuous expansions . . .36 



f An oval aperture, larger than the orifice . . 33 



' \ No aperture . . . . . .34 



f A tubular process below the aperture, in some cases : zooecia very 



33. 4 narrow below . . . Eucratea chelata, var. repens 



y No tubular process below the aperture . Membranipora 



f Peristome much raised below, collar-like . . Phylactella 



' \ Peristome not much raised below . . . .35 



f Zooecia minute, much narrowed below. Orifice small, usually with 



35. 1 a sinus ..... Hippothoa 



[ Zooecia not narrowed below. Orifice with a sinus . Schizoporella 



{ Zooecia partly separated by a thin calcareous crust. Colonies 

 36 J small . . . . . . .37 



[ Zooecia contiguous . . . . . .38 



f Zooecia pear-shaped. Orifice with a sinus . Hippothoa expansa 

 37. 1 Zooecia ovoid. Orifice subcircular, with a tubular peristome 



y ' Lagenipora socialis 



' Orifice close to the upper end of the zooecium (unless crowned by an 

 ovicell). Front of the zooecium marked by transverse or 

 radiating furrows or lines. The very young zooecium may 

 possess a membranous area, which becomes roofed in by the 

 union of two lateral series of converging bars (Fig. 257) . 39 

 Characters not as above . . . . .40 



r Furrows with uniserial rows of pores (often minute), which are rarely 

 irregular . . . Cribrilina (Fig. 257, A) 



39. \ No rows of pores. Distinct transverse lines or spaces and a 

 median longitudinal suture between the bars 



Membraniporella (Fig. 257, B) 



38. 



