37 



marine bed, but they are the principal forms that make up the 

 lower marine bed. The altered distribution of these two species 

 in our local sea-areas marks an important interval of time — a 

 measure of time that must have been sufficiently long to 

 permit of a gradual change of conditions that led up to the 

 total extinction of one species and local limitations of another 

 species, in South Australian waters. 



A sample of the lower marine bed was washed and on 

 examination the following foraminifera were noted : — 



Miliolina secans, d'Orb. ; M . circularis, Bornem. ; M. 

 undosa, Karrer ; M. boueana, d'Orb.; M. oblonga,, 

 Montagu. 



Triloculina trigonula, d'Orb. ; T. tricarinata, d'Orb. 



Spiroloculina grata, Terq. 



Pulvinulina repanda, Fichtel and Moll ; P. punctulata,. 

 d'Orb. 



Rotalia beccarii, Linn. 



Polystomella crispa, Linn. 



The above are all shallow-water forms, but scarcely 

 typical of estuarine conditions. Polystomella crispa is in great 

 numbers, and Triloculina trigonula and Rotalia beccarii, 

 although not so plentiful as the first named, are common 

 forms in the material. All the species present are represented 

 by strongly built examples and are more typical of open sea 

 conditions than a brackish estuary. On the other hand there 

 is a remarkable absence of some of the commonest species 

 which occur in the shallow waters of our present seas, more 

 especially Nubecularia, which is the commonest foraminifer 

 of our coasts and, in most gatherings, number more than all 

 the other foraminifera together — yet not a single example of 

 this form was observed in the Dry Creek material. In addi- 

 tion to the foraminifera several species of Entomostraca 

 (Ostracoda) were noted. 



All the shells contained in this bed were honeycombed 

 by boring organisms to an unusual degree. Many of the shells 

 had been perforated to such an extent that scarcely any por- 

 tion of the shell preserved its solid form — and every shell 

 appeared to have been more or less attacked in this way. 

 The parasitic intruder was probably the minute boring sponge, 

 Cliona, which makes a host of any shell or calcareous rock 

 that it may find handy to utilize for this purpose. The 

 waters, at the locality referred to, must have supplied con- 

 genial conditions for the development of this particular 

 organism. 



The geological section at Dry Creek shows a close accord- 

 ance with similar sections that have been exposed in excava- 



