some Species of ^iiixdreiporsi. 195 



A specimen of a peculiarly growing Madrepora, from 

 Madagascar*, exhibits the required structures very plainly. 



The colony is large, flat, with a thick central expansion 

 terminating circumferentially in short, thick, coalescing 

 branches, covered above with numerous secondary branchlets 

 which are very proliferous. The upper surface of the central 

 part has many low, stout, and a few taller, sharp-pointed, 

 proliferous branchlets, and at their bases and all around them 

 are somewhat sunken surfaces crowded with immersed calices. 

 There are others on the branchlets and around the little crowds 

 of buds which give them an irregular appearance. 



On the back of the colony the number of calices gradually 

 diminishes from the ends of the branclilets to the centre, 

 where they are few, wide apart, and some on low oblique 

 projections, and the others are immersed and small. 



There is a considerable difference between the immersed 

 calices on the under and upper sides of the colony. Those on 

 the first-mentioned surface are very small, wide apart, and 

 present no septa at the slightly raised margin, which usually 

 has some well-developed spinules close to it ; whilst those on 

 the upper surface are often crowded, slightly raised at the 

 margin, and have six septa visible, but small, not projecting 

 far into the calice, and some are not made up of lamellae, but 

 consist of a series of spinules. 



The lov/er calices are the terminations of short corallites, 

 and they pass (in the normal direction of the colony) outwards 

 and downwards, from the proximity of long corallites which 

 traverse the thickness of the dense central part of the colony, 

 running towards the periphery, and keeping nearer the lower 

 than the upper surface. 



The calices on the upper surface are continuous with coral- 

 lites which are long, nearly straight, curving deeply down 

 only near to the long corallites that are in relation with the 

 lower corallites. These upper corallites are separated by small 

 amounts of sclerenchyma, the nature of which is very inter- 

 esting, for it explains the method of the simultaneous growth 

 of the colony as a whole, and of the corallites also. 



The corallites of the immersed calices are close, and their 

 walls are well defined in longitudinal sections. Between 

 the neighbouring corallites, the colligating structures are in 

 successive layers, or storeys, of laminas separated by rows of 

 small, irregular, and short pillars. The laminae are stout and 

 somewhat curved, and the pillars may be stout or slender, 

 this last condition being noticed near the surface of the colony, 

 and the other lower down in the mass. The nature and origin 

 * Probably a variety of Maclrepora cytJwrca, Dana. 



