32 Prof. P. M, Duncan oti the 



is a thin dissepimental looking circle at the junction of the 

 costffi and septa, in .places raised higher than the septal ends. 

 Original width 5 millim. 



The septa reach from the foreign body to which the coral 

 is attached but a very slight distance upwards ; there is no 

 true basal structure. The axial si)ace shows the stone at its 

 base, and it is clear that the septal apparatus and its asso- 

 ciated costal structures were the first parts of the skeleton. 



2. (PL V. fig. 11.) 



A young, flat, discoid corallum, upon the side of a Podoseris 

 elongata. The base is nearly circular at its edge, and the 

 coral then slopes very slightly upwards, being covered by 

 costffi, to the calicular margin. The calice is sunken close to 

 its margin and the columella is raised above the level of the 

 rest of the calice and is formed by the inner ends of the 

 longest septa. 



The calicular margin is broadly elliptical and is recognized 

 easily in places, and elsewhere is produced by close synap- 

 ticulffi. 



The septa are narrower than the costee, and some are very 

 much smaller, unequal, irregular, long, and wavy, others 

 rudimentary ; close to the costaj there are seventy-two, and 

 eight reach the columella, or, rather, form it. Some septa 

 crooked, most uniting, and some bifurcating, the junction may 

 result either in a narrow or a tiiick septum. The costte are 

 not so numerous as the septa, slope widely upon the support- 

 ing body, are subequal to very unequal, usually nearly 

 straight, projecting, but slightly rounded, or flat or swollen 

 here and there, close to touching, some bifurcating, united by 

 transverse or oblique synapticulse ; the narrow intercostal 

 spaces correspond with interseptal spaces. 



Height about 2 millim, long diameter, 8 millim., short 

 diameter of the calicular part 5 millim. and its long diameter 

 6 millim. 



It is evident that the septa and cost^ spring from the sup- 

 porting foreign body xoithout any intervening basal structure. 

 The septo- costal cyclical number is attained very soon after a 

 moderate breadth has been reached. 



Remarks upon some Morphological Details. 



The septa of the species are solid, unilamellar, and are 

 formed by spicules which pass from within the septa out- 

 wards to their surface from definite centres or nodules. Often 



