CATALOGUE 



OF 



MADREPORARIA. 



Volume iv. 



THE MADREPORARIAN FAMILY PORITIDJE 

 (GONIOPORA AND PORITES). 



INTRODUCTORY REMARKS. 



This volume is the first instalment of the result of nearly five years of work on the Madre- 

 porarian family the Poritidse, which of all is probably the most difficult to understand. In it, 

 what is called the porosity of the skeleton reaches a climax, with the result that all the 

 characteristic morphological features of the Stony Corals lose their distinctness. Instead of a 

 corallum built up of many clearly cut calicles with conspicuous septal lamellae, we have to 

 deal with skeletal networks from which, in extreme cases, all the typical radial symmetry may 

 have disappeared. 



Before any progress could be made with such a group, these complicated morphological 

 details had to be worked out. This was necessary in order to form a clear conception of the 

 connections between this type of Madreporarian skeleton and other better known types — better 

 known, that is, because more easily understood. No trustworthy results as to the essential 

 characters of any form of life can be obtained from examination of a few stray specimens 

 alone. The range of variation of all the available specimens, recent and fossil,* requires to be 

 studied, and then what is essential and what is not essential become slowly and gradually 



* But for the light thrown by fossil forms, many of the most important morphological features 

 of this genus, on which the systematic description must be based, e.g. the septal formula, would 

 probably not have been discovered. It is gratifying to be able to record this, because this is the 

 first volume of the Madreporarian Catalogue in which, by special instructions of the Director, 

 Professor E. Ray Lankester, the genus has been treated as a whole, irrespective of the fact that many 

 of its representatives are now only known as fossils. ■ 



B 



