1897.] NEW YORK ACADEMY OF SCIENCES. 171 



quartz, gneiss, etc., with indications of a porphyritic andesite 

 and perhaps dolerites. 



On the way to the coast I noticed that a great deal of drift 

 material at the foot of, the Sierra Nevada mountains showed 

 flattened surfaces with grooves across them like the marks of 

 glacial ice. That glacial ice had once been at this point seemed 

 hardly possible, yet tbe grooves were very much like it. In 

 this locality the rains are excessive at one period of the year 

 and the hot sun of the tropics exerts a weakening influence 

 almost as active as the action of frost in northern countries. 

 The mountains are usually steep along their southern exposure 

 and the material lying below them indicates a heavy erosion and 

 I think it probable that in place of glacial ice at this locality 

 the broken material, on coming down the mountain, assisted by 

 the heavy rains, wore grooves and smooth surfaces on the ex- 

 posed rocks, parts of which were later broken or stripped from 

 the steep mountain sides and brought down with the eroded 

 material. 



The higher elevations of the Sierra Nevada mountains are 

 covered with snow and ice with one or two glaciers, but to sup- 

 pose that heavy material such as was lying at the foot of the 

 abrupt steep ridges of the outer range of mountains had come 

 from the interior glaciers is going a long way for an explanation. 



Further on I passed a small district almost opposite the Cer- 

 rajon mountains where there were low ridges extending from 

 the Sierra Nevadas. They were covered with float rock contain- 

 ing fossils of Cretaceous age, notably large ammonites. These 

 rocks were in many cases of broken, irregular shapes showing 

 little trace of aqueous erosion, others were well-worn and were 

 like the general float material of the valle}'. Much of the broken 

 limestone at this point was of a darker gray and coarser texture 

 than that in the other parts of the valley, and may indicate a 

 Cretaceous system at the base of the Sierra Nevadas, but I found 

 it apparenth' lying on a Tertiary deposit because the soft clay 

 shales and lignite coals were all in place similar to and conform- 

 able with the other parts of the valley. Cretaceous deposits might 

 have been near by at the base of the mountain, and from there the 

 material noted could easily have come. This and localities in 

 the Black Andes were the only places in which I noticed fossils 

 that appeared certainly older than Miocene. Parts of the Black 

 Andes and some small deposits at the foot of the Sierra Nevada 

 mountains have been reported on by other explorers as being of 

 the Cretaceous system, and, as it is found on both sides of the 

 valley, it is possible that the strata extend under it, indicating 

 that this valley was a salt water bay in late Cretaceous times. 



