MADREPORARIAN CORALS 



87 



calices are about i mm. in diameter and project slightly 

 and obliquely from the surface so that the disc of the polyps 

 when expanded is directed upwards towards the apex of the 

 branch on which they are situated. There are six thick 

 but rather narrow primary septa, and in some calices six 

 thinner secondary septa can be seen. The most prominent 

 feature of the calyx is the 

 strong pillar-like columella. 



The cavity of the calyx is 

 shallow and shut off below 

 by a thin calcareous plate. 

 Below this plate the corallum 

 is pierced by a long cylindrical 

 pore divided into a number 

 of chambers by transverse 

 tabulae (Fig. ^^y). According 

 to some authors the endotheca 

 is in the form of irregular 

 dissepiments, and possibly it 

 varies in different species or 

 in different conditions, but in 

 the specimen from which Fig. 

 ;^y was drawn the pores were 

 distinctly tabulate. 



The polyps of Stylophora 

 possess twelve capitate ten- 

 tacles, six larger and six 

 smaller ; and there are almost 

 invariably twelve mesenteries, 



of which two pairs are directives. The polyps are connected 

 with one another by a thin coenosarc, which lies entirely 

 above the coenosteum, and in its lower layer there is a 

 network of canals running between the tubercles as in 

 Seriatopora. 



Family 7. Madreporidae 



The corals belonging to this family constitute the most 

 dominating feature of modern coral reefs, and probably 

 contribute, by the activity of their polyps, a larger propor- 



FiG. 37. — Stylophora. Upper 

 figure showing the surface of the 

 coral. Lower figure showing the 

 calices in vertical section, x circa 25 

 dianis. 



