THE GENUS ALYEOPOKA. 'WITH THE FATOSITID^. 507 



differences whicli need not now concern us, and I propose to 

 deal with these fully in the 4th vol. of the Museum Catalogue 

 on which I am now engaged. 



The Poritidse thus aj^pear to me to establish their claim to 

 stand at the extreme end of the septate thecate series, as per- 

 forate corals ]iar excellence. Their nearest rivals are the 

 Madreporidas, in which the lamiuate septa with their sjnapticular 

 junctions not infrequently dissolve down into a reticulum ; this 

 reaches au extreme in the genus Moydipora. The fundamental 

 distinction between the Madreporidae and the Poritidae appears 

 to lie solely in the fact that in the former the septa are typi- 

 cally laminate however much the lamination may have been 

 secondarily obscured, while in Forites the septa are typically series 

 of trabeculse. 



The problem as to the relatioaship between these two great 

 recent families has still to be worked oiit. It may be stated 

 briefly as follows : — Are the trabecular septa secondary modifica- 

 tions of the laminate or vice versa ? or, again, are they t«vo 

 independent developments (that is, infoldings) of the primitive 

 epithecate skeleton, in both cases leading to the flattening out 

 of the primitive cup as here suggested (cf. tigs. 6-9)? The answers 

 to these questions will most likely come from palgeontology. I note 

 that Miss Ogilvie is inclined to class the Poritidse separately ; and 

 it cannot be denied that the series of comparatively speaking low 

 trabeculae which form the septa suggest the persistence of a 

 primitive character. I do not see that we have enough evidence 

 at present to enable us to come to any definite conclusion. 



Further Notes on the Fhylogenetic Development of the 

 JSladreporarian Skeleton. 



Thecal formations. — We have noted (figs. 9 & 10) two ways in 

 which internal skeletal walls have been built up, replacing the 

 original external epithecal cup. These internal walls have been 

 called thecso, although I am convinced that they have had very 

 difi'erent origins, and it will in the future become necessary to 

 distinguish these differences in any natural classification of the 

 Madreporaria. 



The dissepimental theca (fig. 10), which I should like to suggest 

 might afford the diagnostic character of the Astrseidae, is a very 

 different thing from the synapticular theca (fig. 9), using the word 

 syuapticula for any fusion across the iuterseptal space due to local 



