674 P. MARTIN DUNCAN ON SOME AUSTRALIAN FOSSIL ALCYONARIA. 



occurs. Usually, however, the Mopsece have extremely slender 

 polyparites ; so that probably all stout and simple calcareous bodies 

 belonging' to the Isidinaa should be classified as belonging to the 

 genus I sis. 



The striation on the surface of the calcareous body consists of 

 ridges and furrows of varying distinctness : they may be almost 

 absent or very deeply marked. It is necessary to remember that 

 this ornamentation is carried onto the upper and under part of the 

 calcareous body, coming more or less to a point there ; so that those 

 surfaces greatly resemble worn calices of simple true corals. The 

 furrows are continuous with the water-system of the Alcyonarian, 

 and are the homologues of the striation of the Red Coral (Corallium 

 rubrum) as well as of the costal furrows of Madreporaria. 



Group 1. Calcareous bodies somewhat constricted, short, branch- 

 ing ; ridges distinct and bifurcating ; furrows crossed here and there, 

 and moderately deep ; colour reddish or yellow. A root of this kind 

 is amongst these specimens. PL XXXVTII. a. figs. 5-7. 



Group 2. Calcareous bodies very short, elliptical in outline ; fur- 

 rows deep ; ridges wide. PL XXXYIII. a. fig. 4. 



Group 3. Calcareous bodies short, slender, or very short, circular 

 in outline ; furrows and ridges rudimentary. PL XXXVIII. a. 

 figs. 1-3. 



The specimens of the first group are allied to Isis Jiippuris (Ellis 

 & Sol.) ; those of the second resemble somewhat Isis corallina (Mor- 

 ren), a fossil form of the Calcaire de transition du Groningue (Milne- 

 Edwards & Jules Haime, Hist. Nat. des Corall. vol. i. p. 196) ; and 

 the third group of specimens resemble those of Isis coralloides (Ed. 

 & H.) of Oceania. It must be understood that these resemblances 

 are of no great value, as they only refer to one portion of the orga- 

 nism, which probably is very variable. 



The species of the genus Isis live in moderately deep water ; but 

 it is evident that specimens may be carried away from their proper 

 location and torn to pieces by the currents, and probably by waves 

 the result of great submarine disturbances. Occurring with Amplii- 

 lielice and Balanopliyllice and Polyzoa, these specimens indicate a 

 bathymetrical zone of some hundreds of fathoms. All the specimens 

 come from the coralline zone of the Cape-Otway section, or bed 

 No. 3 ; and they are in the collection of the Geological Society. 



EXPLANATION OF PLATE XXXVIII. a. 



Australian Fossil Alcyonaria. 



Figs. 1 , 2, 3 belong to group 3. Fig. 1 ( X 3), top view ; figs. 2 ( X 4) & 3 ( X 2), 

 side views of calcareous bodies. 



4 belongs to group 2. Top view of calcareous body. Twice nat. size. 



5 & 5 a. Side and top views of calcareous body belonging to group 1. Twice 



nat. size. 



6. Branching form of calcareous body. Twice nat. size. 



7. Basal portion of an Alcyonarian, nat. size. 7 a. Portion magnified 



two diams. 



