OCCURRENCE OF A SUBMERGED FOREST. 167 
alluvials on either side have had their surface artificially raised 
with material excavated from the canal, as shown on the sections 
accompanying this paper, (Plate g, fig. 1.) As the original 
level of the swamp was there at, or a trifle below, that of mean 
high water, and as the canal has been excavated to a depth of 
fifteen feet below mean high water, it follows that a section of 
that thickness (fifteen feet) is exposed to view in the banks, 
wherever they have been cut down to the full depth, and have 
not yet been concealed by the fascine work and stone pitching 
with which the sides of the canal are being lined, from three feet 
below low water to the top of the embankment. 
The nature of the strata observed by us is shown on figs. 1 - 2, 
of Plate 9. (a) The uppermost stratum is a bed of sandy peat 
from nine inches to one foot in thickness, obviously of recent 
origin. (b) Next in descending order are layers of blown sand, 
with interstratified peaty partings, the whole having a thickness 
of about three feet. The outcrop of these beds is stained yellow 
and orange by a superficial film of sulphate of iron and alum. 
(c) A well marked horizon follows where marine shells are plentiful 
especially Anomalocardia trapezia. The bed was traced by us 
almost uninterruptedly from the dam above Rickety Street for 
nearly half a mile north-east. The shells are imbedded in sandy 
clay. A few varieties only, and all belonging to living species, 
are represented. The bed is two feet thick, and at its base is 
from one foot below mean low water to about two feet above. 
(d) A second layer of peaty loam passing in places into true peat 
With roots of various trees, and a few stumps of Swamp Mahan 
underlies the shell bed just described, 
On the longitudinal section the stump of a ee (No. 3 oe 
is shown on the horizon of this bed. No. 3 Stump was in pieces 
When seen by us. It was surrounded with sand containing part- 
ings of peaty matter, covered with a thin sandy clay. This stump 
was one foot seven inches above low water mark and possibly not 
im situ. The exterior showed traces of perforation by a boring 
ae Spheeroma verrucauda, Dana. An alhiast eeeiet 
