SUBCLASS II 



HEXACORALLA 



107 



Porites Link (Fig. 170). Massive or branching coralla. Calices shallo-w, 

 polygonal ; septa irregularly reticulated, usuall}^ twelve in number ; columella 



Fic. 160. 



Litharaea websteri (Bowerb. ). Eocene 

 Bay, England, a, Coralluni, natural size ; 

 enlarged. 



Bracklesham 

 h, Four calices 



Fig. 170. 



Pontes incrustans Reuss. Jliocene ; Mo- 

 ravia, a, Tranverse section ; b, Longi- 

 tudinal section. Both figures highly magni- 

 fied. 



papillous, surrounded by a single cycle of pali, the latter five or six in 

 number, and not very distinct from the septal ends. Endotheca exists 

 sparingly, and may be dissepimental or tabulate, or may be mere stereoplasm. 

 Cretaceous to Recent. The genus 6 c 



Porites is one of the most im- 

 portant of existing reef-builders. 



Subfamily C. 

 Alveoporinae Verrill. 



Septa composed of detached 

 trabeciilae, spines, or reticulated 

 lamellae: Theca perforate. Vis- 

 ceral chamber with perforate tabulae. 



i' 







Fig. 



ITl. 



a, Al veoponi spongiO!!a Vansi. Recent; Fiji Islands. Longi- 

 tudinal section of corallite showing perforate walls and tabulae; 

 h, Alveopora rudis Reuss. Nunimulitic limestone ; Oberburg, 

 Styria, i/i ; c, Calices, greatly enlarged. (Fig. a, after Dana; 

 li, after Ileuss.) 



Alveopora Quoy and Gaim. 

 (Fig. 171). Massive coralla. 

 Calices small, polygonal. Septa 

 represented by detached spinous processes. Tabulae sparsely developed, 

 remotely situated. Tertiary and Recent. 



Koninckia E. and H. Cretaceous ; Europe. 



Family 4. Acroporidae Verrill. 



Composite, branching, lobate, foliaceous, or massive coralla with corallites embedded 

 in a canaliculated arul reticulated coenenchyma. Septa (6-24) compact, somethnes 

 imperfectly developed. Two long septa often projected from opposite sides and meeting 

 in the centre. 



The genus Acropora Oken {Madrepora auct., non Madrepora Linn., 1758) 

 (Fig. 172), is an important agent in the construction of existing coral reefs, 

 and builds Colonies sometimes of considerable size. It occurs sparsely in the 

 fossil state in Tertiary strata of various regions. 



Actinacis d'Orb. (Fig. 168). Massive or branching coralla. Coenenchyma 

 abundant, gx'anulated ; septa stout, of nearly uniform proportions, columella 

 papillous ; pali in front of all the septa. Cretaceous and Tertiary. 



