126 bulletin: museum of comparative zoology. 



sea much above the level of the plahi. A small caAe 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 Tumhres 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 



