usual gravel-bed being deeply worn into hollows, which are filled up with,
as well as the general surface covered by, sandy and reddish earthy matter:
in one of the hollows thus filled up, the skeleton of the Macrauchenia
Patachonica, as will hereafter be described, was embedded. On the surface
and in the upper parts of this earthy mass, there were numerous shells of
Mytilus Magellanicus and M. edulis, Patella deaurita, and fragments of
other species. This plain is tolerably level, but not extensive; it forms a
promontory seven or eight miles long, and three or four wide. The upper
plains in Diagram 4 were measured by the Officers of the Survey; they were
all capped by thick beds of gravel, and were all more or less denuded; the
950 plain consists merely of separate, truncated, gravel-capped hills, two
of which, by measurement, were found to differ only three feet. The 430
feet plain extends, apparently with hardly a break, to near the northern
entrance of the Rio Santa Cruz (fifty miles to the south); but it was there
found to be only 330 feet in height.

(DIAGRAM 5. SECTION OF PLAINS AT THE MOUTH OF THE RIO SANTA CRUZ.

From East (sea level) to West (high):
Terrace 1. (sloping) 355 Ba. M. Shells on surface. 463 Ba. M.
Terrace 2. 710 An. M.
Terrace 3. 840 An. M.)

On the southern side of the mouth of the Santa Cruz we have Diagram 5,
which I am able to give with more detail than in the foregoing cases.

The plain marked 355 feet (as ascertained by the barometer and by angular
measurement) is a continuation of the above-mentioned 330 feet plain: it
extends in a N.W. direction along the southern shores of the estuary. It is
capped by gravel, which in most parts is covered by a thin bed of sandy