366 Prof. J. Orton on the Geological 



sandstone, the material is so thoroughly comminuted that a 

 pebble is a rarity. The Maranon Indians, upon returning 

 from up the Ucayali and other tributaries, bring home rocks 

 to sharpen their knives. I have seen, however, concretions, 

 nodular and stalactiform, strikingly similar to the marly con- 

 cretions noticed by Darwin in the Pampean mud. 



Previous to the expedition of the writer across the continent 

 in 1867, this vast homogeneous formation along the great 

 river had not yielded a single fossil. In the words of Professor 

 Agassiz, " Tertiary deposits have never been observed in any 

 part of the Amazonian basin." And it was on this negative 

 evidence mainly that the distinguished naturalist hazarded the 

 conjecture that the formation was drift*. But the banks of 

 the Maranon prove to be highly fossiliferous. At Pebas, near 

 the mouth of the Ambiyacu, I discovered in one of the beds 

 of blue clay, 12 feet below the surface, a multitude of fossil 

 shells. Below this bed is a seam of lignite, and then another 

 layer of fossils. I engaged Mr. Hauxwell, an English col- 

 lector, to search for other localities ; and in 1870 he reported 

 a large deposit on the south side of the Maranon, below Pebas, 

 at Pichana. The shells were larger and more plentiful than 

 at Pebas, and were found from 6 to 20 feet beneath the soil. 

 In revisiting the Amazons in 1873, 1 discovered at Iquitos, 

 more than a hundred miles west of Pebas, a still more prolific 

 bedf. Here the shells occur above, below, and in the lignite 

 band, beginning about 20 feet from the surface. They are 

 best exposed about two miles below the town. A well dug at 

 Icpiiitos shows : — first, 7 feet of variegated clays, 9 feet of fine 



* The history of the attempt to find the traces of glaciation in this 

 equatorial region is short. The Cambridge professor, who had berated 

 other naturalists for theorizing- without facts, entered the mouth of the 

 Amazons for the first time in his life with the confidence of a prophet, 

 foreordaining boulders, moraines, striae, and all the other appurtenances 

 of a gigantic glacier. All proved to be imaginary ; yet the chief and 

 his satellites stoutly kept their original faith. Professor Hartt, after 

 propounding several modifications, the last one being- the possible glacial 

 origin of the superficial layer (to which the Pebas shells had driven 

 him), finally owns that, " having no evidence whatever of the former 

 existence of glaciers in the Amazons, the question of the glacial origin 

 of the valley need not be raised." For evidence against the supposition 

 of a glacial epoch at the Equator, see 'Ann. & Mag. Nat. Hist. 1871, 

 vol. viii. p. 297. Keller, in his late exploration of the Madeira, searched 

 diligently for erratic boulders ; but not a trace of the " foundlings " could 

 he discover. " I never believed for a moment," writes Mr. Darwin, " in 

 Agassiz's idea of the origin of the Amazonian formation." 



t It is very singular that Castelnau and Herndon overlooked the 

 shells at Pebas, since they are plainly exposed — and still more strange 

 that Mr. Steer, who examined the beds at Pebas and Pichana in 1871, 

 found nothing at Iquitos, where I found shells even more abundant 

 than below. All the known localities were discovered by myself and 

 bv Mr. Hauxwell, under my instructions. 



