36 RECORDS OF THE AUSTRALIAN MUSEUM. 



Obx. — Tlie large size of the corallum in the first instance, and 

 that of tlie corallites in tlie seccnd i-enders this a conspiciious 

 and striking coral. It is composed of a series of closely 

 ahutting polygonal corallites defined on a weathered surface 

 by grooves whicli are not the external manifestation of corallite 

 walls, but simply mark the boundaries of each corallite, and 

 in some conditions of weatheritig become exsert. Notwith- 

 standing this close contact the corallites are not firmly united 

 latei'ally, but remain sepai-ate and distinct and on percussion 

 fall apart. 



Each corallite is coixiposed of an outer or peripheral zone of 

 superimposed small arched vesicles, which inwardly merge into 

 highly inclined lenticnlai- vesicles forming tlie sides of the 

 calices and viscei-al chambers, passing more or less horizcmtally 

 across the lattei', the uppermost forming tlie bare centi-al 

 tabulate area. The constant repetition of this sti-ucture gives 

 rise, in weathered specimens, to a series of irregularly 

 invaginated cups, the lai-gest corallite observed measuring two 

 and a half inches in its longest diameter. Within tlie 

 boundary grooves the surface of each cornllite slopes slightly 

 inwards to form a pei'ipheral area arouml llie centT-al deeper 

 poj'tion, or calice pro[)er, tlie whole HssuniiiM.;' n nioi'e or less 

 funnel-shaped appearance. 



The weakly developed laineHur septa only extend for a 

 coni{)aratively sliort distance over the calice floors ; the iiuiiiber 

 of lamellie is unknown. 



The tabuhe proper, /. c the flooi's within tlie visceral chambers 

 are incomplete, they do not individually extend fi'om side to 

 side, but are formed by lenticular vesicles, and mei-ge into 

 those arcmnd the peripheries ; this tabulate area is, as a rule 

 from half to three quartei's of an inch wide. 



Thin sections piepared for the microscojie reveal but little 

 more than the features already described, it is, therefore, un- 

 necessary to refer to these in detail. In the tiansverse section 

 figui'ed, it will be noticed that the short lamellar sejita are not 

 traceable on the vesicles surrounding the viseral chambers, and 

 are only seen on the exterior of weathered specimens. Sections 

 taken in Imtli directions display the discontiuucnas development 

 of the walls. In places there certainly appears to be a wall 



