19) MADREPORARIA, 
(e) Napopora. 
This genus was established by Mr. Quelch * for a specimen of Porites, which was brought 
back by H.MS. ‘Challenger’ from Tahiti, It is not only a ccenenchymatous form like those 
formerly included in Synarea, but the porous intervening tissue mounts into ramparts. 
Swellings of the ccenenchyma were already known, e.g. in Dr. Klunzinger’s Synarea (= Porites) 
undulata. But these were unusual, and Mr. Quelch was misled into describing the coral as 
showing “intra-calicinal gemmation,” and “almost a meandrine condition.” At the same time, 
however, Mr. Quelch remarked upon a resemblance of the form to one of his own “species” 
of Porites (Jatistellata). Newly acquired specimens have now indeed established beyond doubt 
that the type of the genus is merely a specimen of this same “species” (see P. Society 
Islands 2), and consequently the genus falls back into Porites. 
In the meantime the genus had been accepted by Martin Duncan in 1884,f but was 
merged with Porites in 1899 t by the present writer. 
III. MORPHOLOGY OF THE SKELETON. 
The general description of the Poritid skeleton has been given in detail in Vol. IV., 
pp. 18 et seq., and it will apply here. A very brief summary of it must therefore suffice, for 
our chief duty is to explain the special characters of the genus Porites. The Prototheca § in 
the Poritids, as in the Madreporide, is early flattened out, and the perforate septal plates rising 
from the epitheca are joined by synapticular bars so as to form a reticular theca. The cavity 
of this theca is filled up more or less completely with tissue derived from the fusions of bars 
or teeth from the septal edges with a central trabecula, and these with the occasional develop- 
ment of synapticule forming rings round the fossa together constitute a columellar tangle. 
This may fill up the whole theca, or leave a cup-like depression of varying depth. This 
description applies equally to Porites and to Goniopora. 
The skeleton of Porites differs from that of Goniopora mainly in the fact that, the former 
has only twelve septal plates, while the latter has typically twenty-four. But suppression of 
septa, owing to the diminution in the size of the calicles, may reduce the latter number to 
from twelve to fourteen. No accidental and irregular reduction, even to twelve septa, can, 
however, turn a Goniopora into a Porites; for though the septal formula of the latter can be 
deduced from that of the former, the manner of the reduction is formal and regular. This 
is shown in the accompanying Diagrams (fig. 1). 
The point is of importance, for many small-calicled Goniopore are mistaken for Porites, and 
* Ann. and Mag. Nat. Hist., xiii, (1884) p. 296. 
+ Journ. Linn. Soe., xviii. p. 187. } Op. cit., xxvii. p. 143. 
§ For a detailed account of the use of this term, see Ann. and Mag. Nat. Hist., xii. (1904) 
pp. 1-33. 
