128 MEMBRANIPORID^E. 



CELLEPORA (part.), Hagenow : Reuss : D'Orbigny * (for species with a cal- 

 careous lamina). 



ANNULIPORA (sp.), Gray, B.M. Had. Append. 

 CONOPKUII (sp.), Gray, id. ibid. 

 CALLOPORA (sp.), Gray, id. ibid. 

 AMPIUBLESTRUU (sp.), Gray, id. ibid. 

 MARGINARIA (part.), Koemer : Hagenow. 

 DERUATOPORA (part.), Hagenow. 



GENERIC CHARACTER. ZOARIUM incrusting. ZOCECIA 

 quincuncial, or irregularly disposed, occasionally in linear 

 series ; margins raised ; front depressed, wholly or in part 

 membranaceous. 



THE essential characters of this division are the raised 

 margin, and the depressed front wall of the zooecium, 

 which is always more or less membranaceous. The ori- 

 fice is merely an opening in the membranous portion of 

 the covering, closed in by an opercular valve, and is never 

 surrounded and isolated by a calcareous border. In the 

 most typical forms, such as M. membranacea and M. 

 Lacroixii, the entire area of the zooscium is covered uni- 

 formly by a thin membrane, which lies a little below the 

 level of the margin. In others this membrane is calcified 

 to a greater or less extent, and a solid lamina is thus 

 formed, which protects a certain portion of the cell. 

 But even in species in which this process of calcification 

 is carried furthest, and almost the whole front is hard- 

 ened into a solid wall, its position within and below the 

 marginal rim at once indicates the mode of growth, and 

 reveals the true Membraniporidan structure. The passage 

 to the old Lepralian type is not through such forms, or 

 through the genus Micropora, but through Membranipo- 

 rella, in which the calcareous covering is an outgrowth 



* I have not thought it necessary to swell this list of synonyms by 

 referring to all D'Orbigny's genera, which include species of Membranipora 

 as now defined. The groups to which they belong are given in the family 

 synonymy. 



