I.— INTRODUCTION. 
The fish-remains obtained by Mr. Duns tan from the Ilawkesbury Formation 
at St. Peter’s belong to two distinct series, wbicli are described separately in 
the following Memoir. The first, and much the largest, scries was discovered 
in a dark indurated shale, which splits with a more or less irregular fracture ; 
while the second series was found in a grey mudstone, closely resembling 
that in which numerous fishes occur at Gosford. The skeletal parts of the 
fishes in the first series are actually preserved, though considerably stained 
and partly obscured by the oxides of iron and manganese, with some pyrites ; 
while many of the small cavities in these fossils are filled with calcite. The 
fishes of the second series occur chiefly as impressions on the rock, which arc 
stained black with a thin film of bituminous material resulting from the 
decomposition of the original organic tissues. In both cases the fishes 
appear to have been complete when buried, and show no signs of having 
been disturbed by currents or by predaceous animals. Like most well- 
preserved fossil fishes, they probably denote some local accident which 
suddenly destroyed and entombed them. 
All measurements are given in decimal fractions of the metre. 
8125 
c 
