28 MADREPOKARIA. 



"Litharcea grandis," show a very primitive colony formation, merely small convex mounds on a 

 flattened circular epitheca. This is the simplest form of growth we can imagine, and I 

 assume it to be primitive and just such as would arise from the early budding of an 

 Eupsammiid, that is of some parent calicle in which the primitive epithecal wall had been 

 flattened out and the theca consequently built wholly of septa remaining low and joined 

 into a reticulum by synapticulae. The only corals we know of any size which would 

 supply such a parent calicle are the Eupsammiidae. For instance, an astraeiform arrange- 

 ment of young Stephanophyllia-like calicles with only 24 septa would yield a typical 

 Gonioporan colony. 



In agreement with this origin it is interesting to find in the septal formula of Goniopora 

 a uniform tendency to the fusion of lower cycles with higher, which is one of the character- 

 istics of the Eupsammiidae (cp. Dendrophyllia). The Eupsammiidae and Goniopora appear to 

 have arisen in the mesozoic times, the earliest known Goniopore being from the lower 

 cretaceous of the Crimea, since which time the perforate corals have flourished, belonging for 

 the most part to the tertiary period. No coral said to date from still earlier times and claimed 

 as a Poritid has so far borne the test of examination, that is, of the examination made for 

 this volume and after five years' study of the group (see the list, p. 9).* 



With this origin it is possible to sketch the relationships of the genus with other 

 perforate corals. We start with a parent form not unlike some simple Stephanophyllia with 

 its epitheca flattened and its theca formed by septa, joined by synapticulae and fusing 

 according to a fixed formula. The larger and simpler forms of these corals persist and con- 

 stitute the modern Eupsammiidae. Single forms persist in Stephanophyllia and Balanophyllia ; 

 branching forms in Dendrophyllia and Cmnopsammia ; while the special genus we are 

 dealing with, Goniopora, may be regarded as consisting of astraeiform colonies of the same, 

 arising by very early lateral budding, that is, before the porous septal skeleton rising on the 

 flattened epitheca has grown to any height. Porites may be derived from Goniopora by still 

 earlier lateral budding, for, as shown above, the septal formula of Goniopora passes into that of 

 Porites by the gradual suppression of the tertiaries without any change in order of the septal 

 fusions seen in Goniopora. 



With this origin for Goniopora and Porites, we have cut them once more adrift from the 

 Madreporidae with which we connected them, so long as we thought Porites to be the primitive 

 Poritid. For the origin of the Madreporidae we again look to the Eupsammidae, unless we 

 assume that the epitheca flattened out more than once independently. There is no need for 

 this assumption. The Madreporidae can easily be deduced from dwarfed Eupsammids in 

 which the tendency to rapid growth in height early asserted itself, and the buds were 

 produced above the epitheca and the substratum. 



* What appeared to be a perforate coral from the Silurian was described and figured by 

 Lindstrom, Calostylis. But my own examination of the specimens of this coral in the British 

 Museum has convinced me that it is not a true perforate. Its position in the coral system will be 

 dealt with in a paper on the coral skeleton which I have in course of preparation. 



