124 bulletin: museum of comparative zoology. 



and connecting channels vary from forty-eight to ninety feef and 

 depths of seven and eight fathoms occur in the Rio Valdivia opposite 

 the town. While glacial gravels and boulders not far inland as at 

 Llanco Station show the presence of Pleistocene glaciers or glacio- 

 natant waters, I noted no distinct signs of glacial erosion of the 

 channels about Valdivia. It seems to me more probable, therefore, 

 that these depths indicate a depression of the coast since the formation 

 of the terraces rather than that they are due to glacial erosion inde- 

 pendently of the sea-leAel. 



Below the fifty-five to sixty foot level, I noticed a small terrace on 

 Teja Island opposite Valdi\ia at a height about twenty-five feet 

 above sea-level, but this was not elsewhere observed except possibly 

 as noted below. 



Along the coast south of Corral entrance near Palo Muerto Pt., 

 there are several ancient sea-caves not now visited by the sea at high 

 tide. Near them is a trace of a bench at about 22 feet. The mouths 

 of these caves are not over ten feet above sea-le\el (Plate 33). The 

 bottoms of the caves are covered with a fine dusty cave-earth which 

 covers any pebble bed which may occur on their bottoms. One of 

 the caves (Plate 33) had l)een at the time of my visit recently occupied 

 by natives and a heap of shell refuse formed a considerable mound at 

 the entrance. In the same vicinity at ^lorro Gonzales there is a 

 natural bridge in the rock of the sixty foot terrace formed by a cave 

 penetrating to a small ravine in the rear. In front of the caves at 

 a few points where the coarse Tertiary conglomerate is developed 

 there is a fiat or bench, cut back across these rocks, whose surface is 

 at least partly covered by high tide. It is evident that a slight 

 relative rise has taken place removing the caves from the action of 

 the sea, but while this may have been as much as ten feet it may not 

 have been over five feet as the depth of cave-earth would seem to 

 show. In embayments south of Corral entrance, there are old beach 

 ridges the highest of which comes sharply against the ravined surface 

 of the land behind it. The uppermost of these ridges agrees well with 

 the level of the mouths of the caves and does not indicate a rise of 

 more than ten feet and possibly not more than five feet above sea- 

 level; but, as Suess has pointed out, on the west coast of South 

 America beach ridges may be thrown up by seaquake waves or 

 tsimanus above the normal marine limit and thus are to be taken with 

 caution. 



At Talcahiiano and Concepcion. The literature concerning eleva- 

 tion about the Bay of Concepcion relates largely to the discussion 



