52 STANLEY SMITH. 



Mr. B. Dunstan, Government Geologist, Queensland, has 

 at Prof. Benson's suggestion, very kindly furnished me 

 with topotypesof the species named by Mr. Etheridge, and 

 thus I have been able to compare the New South Wales 

 material with the Australian types and the British forms. 



For the opportunity given to me of gaining fresh know- 

 ledge concerning a group of fossils, in which I am very 

 much interested, my thanks are cordially tendered to Prof. 

 Benson and Mr. Dunstan. 



Definition of Terms. 

 A precise definition of the terms employed is a very 

 desirable preface to any palaeontological contribution. Each 

 group of fossils has its own extensive nomenclature to 

 which additions are continually being made, moreover, 

 authors are not in entire agreement in the use they make 

 of the terms at their disposal. 



The whole coral skeleton is here referred to as the coral- 

 lum. A corallum may be simple, consisting of a solitary 

 corallite, or may be composite, comprising many corallites. 

 A corallite is the skeleton of a single individual, and in the 

 case of a simple or solitary coral, the terms corallum and 

 corallite are synonymous. 



The Rugose Corallite can be divided into two areas, the 

 intrathecal and the extrathecal. The former is built up of 

 tabulae or tabellae, (i.e., smaller and less regular plates 

 ontogenetically derived from tabulae), and the latter of 

 dissepiments. The annular wall formed by the innermost 

 layer of dissepiments against which the tabulae or tabellae 

 abut is the theca. 1 This is usually rendered conspicuous 

 by excessive deposition of calcium carbonate. The corallite 



1 The theca in the Rugose Coral is analogous rather than homologous 

 with the theca in Aporose Corals, which is formed by the dilatation of septa 

 and the union of the dilated portion to form an annual wall. Nevertheless, 

 dilatation of septa does take place at the theca in a few Rugose forms, 

 e.g. Phillipsastraea. Q.J.G.S., Vol. lxxii, (1917) pp. 288-291. 



