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CLASS LAMELLIBRANCHIATA. 
BIBLIOGRAPHICAL REFERENCES. 
1. Tate, ‘‘ Lamellibranchs of the Older Tertiary of Australia,” Part IL, in 
Trans. Roy. Soc., S. Aust., vol. VIII., 1886. 
2. Tate, id., Part II., op. cit., vol. IX., 1887. 
8. Tate, ‘‘ Unrecorded Genera of the Older Tertiary Fauna of Australia,” 
Journ. Roy. Soc., N.S. Wales, vol. XXVII., 1894. 
4. Harris, ‘‘ Tertiary Mollusca of Australia,” British Museum Publica- 
tion, 1897. 
FAMILY OSTREIDZ. 
GENus OsTREA, Linnaeus, 1758. 
O. arenicola, 7Jate, 1, p. 97; Harris, &, p. 300. 
Miocene.—Aldinga Bay, Murray Cliffs (S. Aust.); Gippsland 
Lakes and Shelford (Vict.), doubtful identifications. 
O. hyotidoidea, spec. nov. 
O. hyotis, Tate, 1, p. 96, pl. vi., fig. 5; Harris, 4, p. 229; 
non Linnaeus. 
Now that I have examples of O. hyotis for comparison with the 
fossil oyster of our Eocene beds, which I had tentatively referred 
to that living species, I am induced to regard the two as distinct. 
The fossil species is more depressed, more irregular in outline ; 
the radial ridges less elevated and obtuse, whilst the foliaceous 
scales very rarely develop into tubular spines ; at the same time 
its restriction to Eocene strata implies specific distinction. 
Eocent.—River Murray Cliffs and Aldinga Bay (8S. Aust.) ; 
Muddy Creek, Mornington, Moorabool Valley (Hall and Pritchard), 
and Shelford (Vict.). 
Post-Eocene.—Table Cape (Tasm.). 
O. manubriata, Tate, 2, p. 184; Harris, 4, p. 300. 
Miocene.— Muddy Creek (Vict.). 
O. Sturtiana, Tate, 1, p. 97; Harris, &, p. 299. 
Miocense—River Murray Cliffs (S. Aust.). 
EXCLUDED SPECIES. 
O. hippopus, Tate, 1, p. 98, name preoccupied by Lamarck, 
1818, is, I think, an individual monstrosity of Gryphea tarda. 
Suspcenus GryepHma, Lamarck, 1801. 
G. tarda, Hutton, 1873; id., Tate, 1, p. 98; Harris, 4, p. 302. 
Ostrea hippopus, Tate, 1886. 
EocENE.—Aldinga Bay, Witton Bluff, Chalk-cliffs of the Great 
Bight (S. Aust.); Muddy Creek, Cape Otway, Shelford (Vict.) ; 
also New Zealand. 
Post-EocENE.—Spring Creek (identification doubtful). 
