530 POLYZOA 



/ Avicularian or vibracular zooecia replacing an ordinary zooecium, or 

 J at least situated between the zooecia . . .52 



j Avicularia and vibracula absent, or if present not replacing a 

 \. zooecium . . . . . . .53 



Vibracula present. Colonies small. A pair of longitudinal slits 

 within the area .... Setosella vulnerata 

 52. -j Very large avicularia present. Ovicell closed by a movable lid. 

 Orifice subcircular, with a minute lateral tooth on each side. 



Thalamoporella l (Steganoporella) smittii 



f Orifice semicircular, quite at the upper end of the zooecium ; usually 



with a knob on each side . Micropora coriacea - (Fig. 256, C) 



' 1 A transverse chitinous plate lies immediately below the operculum. 



I A vibraculoid spine may occur . . Megapora rinyens 



Area entirely membranous, usually bordered by spines. 



Membranipora (including Electro, 3 ) (Fig. 256, A) 



54. -| Membranous portion reduced to a small portion, which may be 



variously lobed, enclosing the orifice. 



Membranipora (other species) (Fig. 256, B) 



f Peristome present. No macro . . . .56 



55. 1 Peristome absent ; or if present, with a mucro . . .57 



[(See also Mucronella pavonella, No. 28). 



I' Peristome collar-like, much raised below and at the sides of the 

 J orifice, deficient above. No avicularia . . Phylactella 



I Orifice large, longer than broad. Peristome not deficient above the 

 V. orifice ...... Lepralia 



5>7 ( Wall of zooecium thin, shiny, and without pores . .58 



( Not agreeing with the characters given under No. 58 . .59 



A minute avicularium above the orifice, or where an ovicell is present, 

 situated at the summit of that structure. Zooecia not quite 

 J contiguous. Mucro sometimes present . Chorizopora brongniartii 

 No avicularia. Ovicells on rudimentary zooecia, lying in a plane 

 superficial to that of the rest of the colony. Zooecia long. 



Schizoporella hyalina 



A more or less distinct mucro or prominence beneath the orifice. 60 

 j Mucro rarely present. Orifice nearly always longer than broad, or 



nearly circular, usually large, and slightly indented laterally. 



Lepralia 



/ A tooth projects into the orifice from its lower side . .61 



U- \ No tooth ... .62 



1 Hiucks, J. Linn. Hoc. xxi. 1889, p. 123. 



2 Micropora complanata, Norman, should be placed in the genus Lepralia. See 

 Hincks, Ann. Nat. Hist. 5 ser. xix. 1887, p. 304. 



3 See Norman, Ann. Nat. Hist. ser. 6, xiii. 1894, p. 113. 



