Victorian Fossils. 3 



Ostrea hatchcrU Ortmann, 1897. Amer. Journ. Sci., vol. iv., 



p. 355, pi. xi., fig. 1. 

 Ostrea philitm, Ortmann, 1897. Ibid., p. 356, pi. xi., fig. 2. 

 Ostrea patagonica, von Ihering (non d'Orbigny), 1897. Rev. 



Mus. Paul., vol. ii., p. 221, pi. ix., fig. 2. 

 Ostrea hatcheri, von Ihering, 1899. Neues Jahrb., fiir Min., 



vol. v., p. 8. 

 Ostrea ingens, Zittel, Ortmann, 1900. Amer. Journ. Sci., vol. 

 X., p. 379. Ortmann, 1902, Rep. Princetown Exped., 

 Patagonia, 1896-99, vol. iv., pt. 2, p. 99, pi. xv., xvi., 

 xvii., xviii., xix., figs a-c. 

 Observations. — The fauna of the Miocene or Middle Tertiary beds 

 ^of Victoria and South Australia contains a large form of oyster which 

 lias never been assigned to a definite species. Many examples of 

 these large bivalves are represented in the National Museum fossil 

 collection, but have not been specified up to the present. I am now 

 satisfied, however, that they are Identical with the New Zealand and 

 Patagonian species, Ostrea ingens. 



Professor Tate's useful " Census of the Older Tertiary Fauna of 

 Australia "i mentions on page 249 five species of Ostrea from the 

 older Tertiary (that is, Balcombian to Kalimnan), as understood by 

 Tate. But only four are listed in Dennant and Kitson's " Catalogue 

 ■ of the Cainozoic Fauna," etc. ,2 so that in all probability the fifth in 

 Tate's estimate is that now referred to 0. ingens, Zittel. 



Characters of 0. ingens. — The chief specific distinctions given by 

 Ortmann, and now by the writer, are: — 



1. Large size and extremely thick shell. 



2. Situation of muscular scar. Muscle impression large, 



generally situated a little below the middle of the shell, 

 and a little posteriorly. 



3. Smooth margins of the inner side of the valves, except 



close to the area. 



4. Slight development of the radial folds. In some there is 



a tendency for the lamellae to develop undulae or frills, 

 but with no marked radial disposition. 



This species of Ostrea has been referred by H. Suter to the sub- 

 rgenus Anodontostrea (Suter), 3 the distinctive characters being the 

 smooth inner margin. It seems, however, to belong to Eostrea 

 (Ihering), for the dorsal region of the shell is often distinctly crenate. 



Measurements. — Ortmann gives the length of the largest specimen 

 as 255 mm. and the width as 162 mm. 



The largest specimen in the National Museum collection appears 

 lo be an example from the Janjukian of Bairnsdale, having a length 

 of 218 mm., and a width of 157 mm. Another specimen, from Cape 

 Otway, also from Janjukian beds, measures 180 mm., by 135 mm.; this 

 ■approaches 0. sturtiana, Tate, 4 in its oblong shape, but is very much 



1. Journ. and Proc. Roy. Sec. N.S. Wales vol. xxii., pt. ii.. 1888, p. 2i0. 



2. Rec. Geol. Surv. Vict., vol. i., pt. 2, 1903. 



3. Descriptions of New Tertiary Mollusca, Part I. New Zealand Geol. 

 iSurv. Palaeontological Bulletin, No. 5, 1917, p 86. 



4. Trans. Roy. Soc. S. Austr., vol. viii., p. '97. 



24 



