162 



witli seaweed and sponges, (c) on mud banks nearer shore. 

 2. Brackish pools, covered at spring-tides, lining the margin of 

 the river to the north of Birkenliead. 3. Several small creeks 

 tributary to the main stream on the south side of Port Adelaide, 

 near the Pinery. 



I must not omit to mention a possible source of error in the 

 enumeration of species supposed to be now living in our estuary, 

 arising from the presence of Post-Tertiary marine deposits, ex- 

 posed in the banks, and probably forming the bottom of the 

 stream in some places. Some samples brought up by the dredge 

 were quite valueless for the purpose desired, in consequence of the 

 evident mixture of derived material with the recent forms, and a 

 considerable number of species have been discarded from the list 

 from a suspicion that they w^ere from the fossiliferous beds re- 

 ferred to, and are not represented by living forms in the river at 

 the present time. This only applies to the dredgings in the North 

 Arm ; those secured from the brackish pools and the small creeks 

 to the south of Port Adelaide are free from this source of error. 

 But after the most careful examination with a view to the 

 elimination of doubtful occurrences, some on the list may be 

 proved by further investigation to be foreign to the living fauna. 

 It is not improbable that the North Arm has been an inlet for 

 saltwater dating from Post-Tertiary times, and although much 

 diminished in area, and becoming more land-locked with the shal- 

 lowing of the South Australian littoral, many of the littoral 

 species of Foraminifera may have held their ground in the salt- 

 ^\'ater lagoons of the flats from a period when the coast-line was 

 much further inland. 



MiLiOLiNA, Williamson. 



M. Bouemia, d'Orbigny. A small and neatly-formed shell, 

 ornamented by line longitudinal striae. Widely distributed in 

 shallow waters of temperate and tropical seas. Moderately 

 common on mud bottoms. North Arm. 



M. bicornis, AValker and Jacob. An ornamented shell similar 

 to preceding, but of stouter build and less regular in outline. A 

 few examples taken from seaweed bottom. North Arm. Probably 

 derived. 



J/. Fer'Hssacii, d'Orbigny. Ornamented, with a few conspicuous 

 longitudinal ridges or costa? on each side of test. A widely-dis- 

 tributed form at moderate depths. Rare on seaweed and mud 

 bottoms, North Arm. The robustness of these shells suggests 

 the probability of their being derived. 



J/, circularise Bornemann. A small shell with few, much- 

 inflated segments, and possessing a narrow crescentif orm aper- 



