178 Frnlrrn-h- C/h, pjuo u .- 



(ienus ISIS. LinnacMis. 



Isis COMPHES8A, Duiic;in. (Plate XVII., Kigs. \7n. b\ Pi. XIX., 

 Fi.(. 41). 



Isis r(>/////ressa. Duiicun. 1880, Palaeoii tologia Iiidiea (Siinl 

 Fos.sil Corals and Alcyonaria), ser. xiv., vol. i., pt. 1, 

 p. 109. pi. xxviii.. figs. 4. 5. 



Ohserraf/o/is. — Two fiaiiiuents of the stony axis of the alcyonarian 

 occur in the Mallee Ijoi-es, which are conipai-able to the above foi-m. 

 The largest fragment measures 12 m^ni. in length, and its greatest 

 transverse diameters are 6.25x4 mm. In shape it is a flattened 

 cylinder, and is superficially grooved with coarse longitudinal striae. 

 The fractiired surface of one of the fragments is, in the central area, 

 discoloured to a bluish black, as if by residual organic staining. The 

 articular surface is nearly flat, and has all the characters of 

 Duncan's figured specimen. 



A transverse section of this fossil under the microscope shows it 

 to consist of undulose concentric laminae, with a sub-circular 

 central portion having numerous shoi-t i-adial extensions; and these 

 layers, by accelerated growth along one axis, cause the stem to 

 finally assume an elliptical outline. The cusps of the concentric 

 layers form the costae on the external siirface of the calcareous axis. 



Duncan's specimens were from the Haj beds of Tandra Rahim 

 Khan. 



Occurrence.— Bore 3. 226 feet. Bore 11. 495-500 feet. 



NOTE ON THE (lEXEIJlC AFFINITIES OF THE ABOVE 

 AL( 'YON A R I AN FOSS I LS . 



Calcareous joints of Alcyonarians have long l)een known fioiii the 

 Tertiary beds of Southern Australia and N^ew Zealand. These 

 fossils have hitherto been referi'ed to Is/'s. Tenison Woods in 1862 

 figured a basal joint from the Mount Gambier limestones whicli he 

 referred to that genus. 1 Subsequently Duncan provisionally re- 

 ferred to Isfs and Mopsea the collection of alcyonarian remains 

 sent to him fioni .\ustralia (Cape Otway beds), accordingly as the 

 calcareous joints are bianclied or unbranched.Z '{'hat is to say, if 

 branched, they belong to Isis. if not they may i)elong to Mnpsen. 

 or are unl)i'an(he<l joints of Isis. This view now ap])ears to be 

 erroneous, for in Mo/>sfn encrinii/a l)ranchiiig invariably takes 



1. Geol. Obs. in S. Austvali.i : plate fiiciri-r y. 73, fife'. 6. 



2. Quart. .1. Ceol. Soc, vol. \xxi., p. 07:!. 



