n 
Tho shell of Jj. (?) IVia mniaUemh Avas evidently thin, and it neces- 
sarily follows that tho eroded beaks do not present that marked feature, 
nsnally so characteristic of a ferv families of Pelecypoda, particularly the 
Unionidie. 
LocAilltii. — Messrs. Goodlet and Smith’s Brick-clay Quarries at Crowir- 
strcct, Waterloo, and Snrry Hills, Sydney. 
Horizon . — Ironstone hands in the Wianamatta Shale. 
Collector. — T. W. EdgeAvorth David, Esq., B.A., &c., Geological 
Surveyor. 
Unio Duxstaxi, sp. nor. 
PL I, Figs. 11-19. 
Sp. Char. — Shell narroAV, very transversely elongated, thin and com- 
pressed throughout its length, approaching to linguliform. Cardinal margin 
long and slightly arched, ventral margin comparatively straight, sharp and 
knife-edge like. Anterior end very much compressed, the margin rounded, 
jAosterior end thin, attenuated, and very much compressed toAvards the margins, 
Avhich are obliquely rounded, the posterior-ventral angle being almost pointed. 
Uinbones placed close to the anterior end, small, and laterally flattened; 
flanks of tho shell almost flat ; diagonal ridges and posterior slopes but very 
faintly developed, the latter A^ery faintly concave, and lost in the compressed 
posterior end. Anterior adductor impression fan-shaped, situated very high 
up under the anterior cardinal margin ; umbonal scars \"ery strongly marked, 
tAvo immediately behind the adductor scars in a line, and close under tho 
cardinal margin, the others clustered on the flank ; posterior adduetors faint 
and shalloAv. BaHial line Avell marked, Avith the impression of lil)re scars at 
the anterior end. Ornament of very closely set concentric lines, Avith irregular 
glossy groAvth laminse. 
Ohs . — This is so very distinct from the other shells here described that 
a comparison is not required. It possesses the unmistakable outline of one 
section of the genus Unio, represented by such forms as Unio Grayanus, 
Lea, Id ShejKtrclianus, Lea, and Id follicnlatiis, Lea. There is also some re- 
scml)lance to a European Coal Measure fossil, Anthracosm lateralis. Brown,* 
■* 111. Foss. Conchology, 1S49, p. 177, t. 73, f. 26. 
