a Glacial Epoch at the Equator. 299 



the lack of striation, however, is no proof that they are not 

 true boulders. 



To complete the glacial picture, it is asserted that a gigantic 

 moraine stretched across the mouth of the valley — though, as 

 Dr. Newberry says, " a moraine can hardly be formed by a 

 glacier, except where there are cliffs and pinnacles along its 

 coui-se ;" and as the absence of glacial inscriptions is attributed 

 to disintegration, so it has been found convenient to say that 

 this morainic wall must be looked for in the depths of the 

 Atlantic*. It is worthy of remark, moreover, that fiords, 

 which are conteraiinous witli the drift of high latitudes, are 

 absent from equatorial coasts. Thus we are called upon to 

 believe in the existence of a tropical glacier, 2000 miles in 

 length, moving "for hundreds of thousands of years" over 

 the continent, upon evidence which is singularly defective. 



2. We object to the theory because the formation contains 

 Tertiary shells. Previously to the expedition of the writer 

 across the continent in 1867, the vast clay -beds along the 

 Great River had not yielded a single fossil. In the words of 

 Professor Agassiz, " Tertiary deposits have never been ob- 

 served 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 Upper Amazon prove to be highly fossiliferous. 

 At the confluence of the Ambiyacu with the Maraiion stands 

 the village of Pebas, about two hundred miles west of Taba- 

 tinga, long. 72°. The site is a level tract, about fifty feet 

 above the river ; and the formation is wholly of those peculiar 

 variegated clays which we traced far up the Napo, and are 

 continuous with the Tabatinga beds and with those on the 

 Lower Amazon, where they are overlain by sandstone. Im- 

 bedded in these clays, several feet below the surface, and in- 

 contestably in sitUj we discovered numerous small shells. 

 They were examined by Mr. Gabb, of Philadelphia, who pub- 

 lished f the following species : — Turhonilla minuscula^ n. sp. ; 

 Neritina piqja, Linn. ; Mesalia Ortoni, n. sp. ; Tellina ama- 

 zonensis, n. sp. ; Pachydon ohliquus, n. sp. ; P. tenuis^ n. sp. 



Before leaving Pebas, we engaged Mr. Hauxwell, the ex- 

 perienced English collector, residing at that place, to search 



• It seems to us that if " the waters of the lake were suddenly released," 

 they would have exerted the most denuding force near the outlet ; yet 

 along the Lower Amazon we find vast remnants of the sandstone series, 

 as those of Erere, Obidos, and Almeyrim, while further west the waters 

 seem to have made a clean sweep of it. No table-topped hills like 

 Almeyrim are seen west of Manaos. 



t Amer. Joum. Conch, vol, iv, p. 167, 



23* 



