[Proc. Rot. Soc. Victoria, 32 (N.S.), Pt. I., 1919J. 



Art. II. — New or Little-known Victorian Fossils in the- 

 National Museum. 



Part XXIV.— On a Fossil Tortoisk in Ironstone from 

 Carapook, near Casterton. 



By FREDERICK CHAPMAN, A.L.S. 



(Palseontolo^ist, National Museum, Melbourne.) 



(With Plate I). 

 [Read Stli May, 1919]. 



Note on the Matrix. 



Bog iron-ore, known mineralogically as a form of Limonite- 

 (2Fe'203 -f-SH^O), is a common preservative of fossil plants and 

 animals, in which their remains are usually found as casts and. 

 impressions. In Victoria we have numerous instances of such 

 occurrences of beds of ironstone; as for example, the deposit on the- 

 Parwan Creek, and other exposures near Bacchus Marsh, which 

 contain leaves of Laurel, Cinnamon and Beech. 



Of terrestrial or freshwater (lacustrine) origin, these bog iron- 

 ores contain the remains either of the organisms which were living 

 in the swamps and lakes, as the ostracoda and shells ; or remains^ 

 of animals as bones and feathers, which were washed into the- 

 deposit off 'the land. 



In the case of the Swedish lake iron-ores, the higher ba-cteria 

 have played a prominent part in separating the iron oxide from 

 the water, and such may have been the case with the beds of iron- 

 stone near Casterton in which the above fossil tortoise was found. 

 The iron was in alli probability derived from the vast outpourings- 

 of lava during late Tertiary times in Victoria, being dissolved out 

 by meteoric waters and re-deposited in pans on the bottoms of 

 swamps and lakes. 



Description of Specimen. 



The practically unique fossil now under consideration was found 

 in a bed of ironstone at Carapook, north-east of Casterton. It" 

 represents a replacement in limonite of the greater part of the 

 body cavity of a tortoise. On the dorsal surface the vertebral' 



