IN SOME SERIAL COEALLA. 365 



lobed free upper edge, and it is seen in the axis of the serial 

 corallites. 



The endothecal structures are plentiful, but delicate, arched 

 and thin. One set of dissepiments stretches from one septum 

 to its neighbour on either side in the same serial corallite, and 

 another set is parallel to the flanks of the columella, and extends 

 from it between the nodular points, and comes in contact with 

 the free vertical edge of the septa. The closing of the inferior 

 parts of the interseptal loculi and of the space between the septa 

 and the columella is perfect ; and as the coral grows upwards 

 and outwards, tliere is a succession of floors of arched dissepi- 

 ments formed. The columella is essential, and arises from the 

 endothecal base, whence spring the walls and septa. 



In this instance the epitheca clearly acts as a base of growth, 

 like the solid theca of some compound corals. Its structure 

 resembles that of the protectiye epitheca which is seen cover- 

 ing the walls of many simple corals ; but it is denser within, and 

 yet is very readily removed by force. 



PoRiTEs LUTEA, Quoy Sf Gaimard, Voy. de V Astrolabe, Zooph. 

 1833, p. 249. 



This species is one of the incrusting forms of Porites, or, 

 rather, it has a well-developed epitheca on its large base which 

 covers the substances on which the coral rests, and to which it 

 adheres more or less. 



It is a low form ; and the specimen under consideration is 

 4 inches long, 2 inches broad, and I iuch high in the centre. The 

 edges are thin, and the base is concave, so that the coral is an 

 elongated flat dome in shape. The corallites are about f millim. 

 in breadth, and there are therefore a vast number of them in the 

 corallum. 



It is perfectly evident that all the corallites could not arise by 

 gemmation from one parent, and that nearly all do arise directly 

 from the base of the corallum. 



There is no sclerenchyma made up of a layer of highly trabe- 

 cular tissue which might act as a base for the corallites to spring 

 from. On the contrary, they arise from the upper surface of 

 the epitheca, which was therefore their basal structure when 

 they commenced growth. Subsequently many did bud on their 

 flanks ; but the majority simply grow vertically, or in a slanting 

 direction. 



28* 



