126 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
sea much above the level of the plain. A small cave in the granite 
of the hillside in the public park by its angle of slope into the rock is 
‘ shown to be artificial and having nothing in common with sea-caves. 
A visit to Penco on the north of Concepcion gave little or no evi- 
dence regarding a change of level. ‘The plain of dark sands is here 
wanting, that deposit being largely an ancient delta of the Rio Bio Bio. 
At the north end of Penco Beach, on a point of rock cut off by the 
railway cut from the bluff of Tertiary sandstones which here form the 
shore, at about twenty feet above sea-level I found shells thickly 
strewn in the soil together with fragments of mammalian bone, a 
typical mode of occurrence of Indian shell-heaps. 
Talcahuano and Tumbres Peninsula I have given some account 
of the coast near Tumbres Peninsula in my itinerary (p. 32). There 
are good sea-caves on the inside of the Paps of Bio Bio at the present 
sea-level but none above. The surface of the Tumbres Peninsula is 
covered with a brownish weathered layer containing chips of quartz 
and schist derived from the underlying rock. Waterworn pebbles 
are absent except in situations about to be described as village sites. 
There are sloping surfaces of the bed rock at discordant levels and 
abundant traces of water action in cutting vales, but none of the 
horizontal lines marking the prolonged action of waves in cutting 
cliffs or heaping up beach materials. 
On the southeast side of Tumbres at about 330 feet I found round 
patches of marine shells in the sod of the tosca or surface deposit. 
The shells in the first example seen occupied a space about twenty-one 
feet in diameter in which the grass, in December, of a light color 
because it was dead, showed clearly the shell covered area because all 
about the shell tract a species of sorrel with a reddish stem and fruit 
grew in abundance. This plant avoids the shell deposits probably 
because of the lime. Observing this character of the vegetation, I 
went to other tracts which from a distance showed the absence of the 
sorrel and found them in each case the site of a thin shell deposit. 
One of these shell deposits was upwards of forty feet in diameter. In 
one of these areas I picked up a stone pestle, a cylindrical beach 
pebble battered by wear at both ends. With the shells were a few 
broken beach pebbles which seemingly could have had no use, but 
such pebbles were altogether absent in the weathered soil and tosca 
rock outside of the shell deposits. It is evident that these deposits 
are of human origin. Darwin mentions shell deposits on Sentinella 
Hill at about 400 feet elevation reported to him by Dr. Jenks, the 
Assistant surgeon of the Beagle. At no point on the peninsula was I 
Otis dar Dek, 
