i)7 



3) The colonies, which never Iiave a free, upright growth, are ex- 

 clusively attached l)y radical fibres which either issue from a creeping 

 stolon or from the basal surface of the individual zoa?cia: 



4) the colony is attached by radical fibres which issue from a 

 creeping stolon; (the zoa-cia which issue separately from the stolon, are 

 furnished with two rows of spines, joined together in pairs and separated 



by a single row of transverse slits; no avicularia, no ocrcia. . . StoloneUa Hincks. 



4) the colony is attached by radical fibres which issue from the 

 basal surface of the individual zooecia, and these are generally connected 

 with one another by shorter or longer, wider or narrower tubes to 

 form a network with larger or smaller apertures: 



5) the zooecia very slightly calcified; the connecting tubes between 

 the individual zooecia distinct; ocEcia wanting; as a rule pedunculate, 



freely movable avicidaria lieania Johnston 



(Diachoris). 



5) The zoa>cia strongly calcified; the connecting tubes between the 

 single zooecia indistinct, broad and short, and only visible from the basal 

 surface; ooecia may be present; sessile avicularia; (from each avicularium 

 issues a spine which is often much branched and may conceal a larger 



or smaller portion of the frontal membrane) Hiaiilopora Mac Gillivray. 



3) the colonies have a free upright growth or are incrusting. 



6) The distal part of the zooecia provided internally with two lateral 

 spaces open towards the frontal surface (sometimes combined to one 

 single, horseshoe-shaped space), formed by two calcareous plates which 

 issue from the lateral walls and converge towards the distal wall; 

 avicularia and free ooecia may be present; the colony incrusting or 

 laminate) Cluipcrin Jul lien. 



G) The distal part of the zooecia without lateral spaces: 



7) There is a frontal shield, formed by five broad hollow spines 

 lobed at the edge and separated bj' rows of jiores; (a simple com|)lelely 

 chitinized operculum; sessile avicularia) Petalosteyiis nov. gen. 



7) No frontal shield: 



8) No ocecia : 



9) The distal, broader, more or less .symmetrical part of the zoa'cium 

 is separated from a nearly as long, proximal, narrow, cylindrical part 

 by a constriction: 



10) The ba.sal edge of the distal wall is angular; no avicularia; a con- 

 striction jusl (listally to the distal wall Halophila Husk (Lev. mod.). 



7 



