155 
Horizon and Localities , — This species is not rare in Australia, but 
it is not easy to procure well-preserved specimens of it. According to McCoy, 
it is very abundant in the calcareous sandstone at Loder’s Creek and Korinda; 
Dana says it occurs at Wollongong Point and Illawarra. Strzelecki found 
it at Mount Wellington, Tasmania ; and Mr. Clarke at Pmymond Terrace, at 
the junction of the Hunter and Williams E-ivers, and at iEllalong, on the 
road from Crawford’s Creek to Watagan Creek ; and at Darlington, where it 
is contained in a yellowish- grey, rather friable, calcareous sandstone. It has 
also been found at Muree and Morpeth, in a grey compact limestone, in 
which the substance of its shell, which is nacreous and iridescent, is preserved. 
Productus fragilis, J. Lana} 
PI. X, Fig. 3. 
JProdllctus fragilis, -T. Dana, 1849, Geol. Wilkes’ U. S. Explor. Exped., p. G86, pi. 2, fig. 7. 
This shell is subrectangular, transverse, and a little broader than long. 
The ventral valve is deep, with prominent, more or less geniculated and pro- 
longed, margins ; the dorsal part is slightly sinuous ; the hinge line is as long 
as the transverse diameter ; the ears are depressed at their extremities ; the 
hinge line forms a right angle with the lateral margins ; the beak is small, 
slightly recurved, and only very slightly projecting over the hinge line. The 
external ornamentation consists of a great number of fine longitudinal strise 
crossed by faint concentric undulations. The small ribs produced by these 
striae do not appear to be sjoiny. The muscular impressions are rather close 
to the beak, and are very shallow ; those of the cardinal muscles are very 
narrow, and form irregular ramifications, while those of the adductor muscles 
are relatively broad and composed of a great number of parallel furrows 
with a longitudinal direction, and only very slightly passing below the lower 
limit of the cardinal impressions. On account of the extreme thinness of the 
shell the rest of the internal surface is covered with strise similar to those of 
the exterior, with this difference, that towards the margins they are riddled 
for some distance by small punctures like pin-pricks. The dorsal valve is 
slightly concave, and consequently leaves a relatively small space between 
itself and the ventral valve. Its shell seems to have been a little thicker 
than that of the ventral valve, its interior surface showing no trace of the 
' [Mr. R. Etheridge, .Junr. , considers this form to be synonymous with Prodiictus brachythmrus, G. Shy. 
Geol. and Pal. Q’land, 1892, p. 251. — W.S.D.] 
y 
