
COTTON—SOME TERTIARY Fosstn MOLLuScS 661 
thetidis Hedley 1902, Specimens were picked out of the Salisbury Bore, 330 feet. 
Shells of the palacaretic genera Propeamusium Gregorio 1884, Parvamussium and 
Variamussium are different from the Australian species such as atkinsont which 
belong to Clenumusium Iredale 1929 and there are two Recent species, the geno- 
type C. thetidis Hedley of Eastern and Southern Australia and the deeper water 
(. culacon Tredale 1929, of N.S.W, 
OSTREA ARENICOLA Tate, 
Ostrea arenicola Tate 1885. Trans. Roy. Soc. 8. Aust., $, 97, pl. 10, fig. 6. 
The species was described from the Upper Aldinga series of Aldinga 
(Adelaidean) and is the common oyster and dominaut shell of the Adelaide 
Bores, being plentiful in the aquifer. It is closely related to the Reeent Port 
Lincoln Oyster Ostrea sinuata (—angast) and to the Upper Pliocene, Werrikooian 
Ostrea sinuata glenelgensis Singleton 1941. This species is displayed in the Tate 
Museum at the University of Adelaide from the Abattoirs Bore as ‘Ostrea sp.?’ 
Like most species of Ostrea, it is variable and the ‘extreme variety’’ of O. arenicalu 
mentioned by Tate from the “Upper Murravian"’ at the North-west Bend is 
probably the same species. It seems quite likely that O. sturtiana Tate from 
“the upper part of the River Murray Cliffs, from Overland Corner to beyond 
Blanchetown,’’ is merely a senile form of O. arenicola, as its hinge development 
suggests. The narrow shape may be due to erowded vonditions. The Recent 
QO. sinuata when growing in clusters frequently becomes elongate and develops 
a longer igamental area. Further study would be required to confirm this, but 
if the theory is correct, O. sturtiana has priority. 
Lorua HyoTIDOIDEA (Tate), 
Ostrea hyotidoidea Tate 1899. Trans. Roy. Soc. 8, Aust., 23, 268, 
Tate first identified this fossil species as Ostrea hyotis Linne, which is a 
Recent tropical shell from the Indian Ocean and north Anstralia. He later 
renamed the fossil from the Murray River Cliffs, O. hyotidoidea Tate 1899. Both 
this and the Recent shell belong to the peculiar ‘‘ Coxcomb’' oysters classed under 
the genus Lepha. The fossil has been recorded from the Adelaidean, but so far 
T have not seen it in the bores examined. 
NEOTRIGONIA TRUA Sp. nov, 
Plate xx, fig. 5-6. 
Shell trigonal, compressed ribs, twenty eight, narrow set with close, fine 
lamellae ; anterior margin convex, dorsal at first slightly convex, then concave and 
