P. MARTIN DUNCAN ON SOME AUSTRALIAN FOSSIL ALCYONARIA. 673 



48. On some Fossil Alcyonaria from the Australian Tertiary 

 Deposits. By Professor P. Martin Duncan, M.B., F.R.S., 

 Y.-P. Geol. Soc, &c. ("Read June 9, 1875.) 



[PlateXXXYIII.a.] 



Amongst the collection of corals which was submitted to me for 

 examination from the Tertiary beds of Cape Otway in Victoria, were 

 some specimens of Isidinse. My memoir on the Possil Corals of the 

 Australian Tertiary Deposits, which was published in the Quarterly 

 Journal of the Geological Society, vol. xxvi. 1870, p. 284, did not 

 allude to these Alcyonaria. Now, however, it becomes necessary to 

 examine and describe them ; for there are Tertiary beds in New 

 Zealand which contain somewhat similar organic remains (Quart. 

 Journ. Geol. Soc. vol. xxix. p. 375). The Cape-Otway Tertiaries 

 were described in the above-mentioned communication from the 

 writings of Messrs. Daintree and Wilkinson, of the Geological Survey 

 of Yictoria ; and I ventured to correlate them with particular Tertiary 

 deposits elsewhere in Australia. 



Amongst the most interesting of the strata of the Cape-Otway sec- 

 tion was that called No. 3, or the Upper Coralline bed. It contained, 

 besides Amphihelia incrustans (nobis) and Balanojphyllia Selwyni 

 (nobis), the specimens about to be noticed. Being the equivalent 

 of the Poiyzoan limestone of "Wood, which is of Mount- Gambier age, 

 it is a deep-sea deposit, and covers an important series of shallower- 

 water deposits. It is younger than they are, and forms the Upper 

 Miocene of Daintree, the Crag of Wood, and my Upper Cainozoic 

 stage. 



The specimens may be divided into three groups, which have a 

 specific significance. In one the Isidian characters are well shown, 

 and the furrows on the calcareous bodies are well developed ; in the 

 second the bodies are short, irregular, and deeply furrowed ; and in 

 the third they are both long and short, and very slightly furrowed. 

 They are formed of the solid calcareous knots which exist in all 

 Isidinae, and which in recent forms are connected above and below 

 by a horny tissue, which probably is not preserved by fossilization. 

 The genus Isis may be distinguished as follows : — The polyparite 

 has an axis composed of polype-bearing pieces of carbonate of lime, 

 united together by disks of an elastic horny substance. The calca- 

 reous bodies form little trunks or columns varying in height and in 

 the amount of external striation. The branches commence from the 

 calcareous bodies, and not from the horny matter. 



It is this branching from the calcareous body which distinguishes 

 the genus Isis from Mopsea, in which the branching starts from the 

 horny substance. Hence, if branching calcareous bodies are found, 

 they may be safely attributed to the first-named genus ; but if cal- 

 careous bodies without branches present themselves, they may be- 

 long to Mopseoe, or to parts of species of Isis where no branching 



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