n Glacinl Kporh at the Equator. 299 



the lack of striatioii, liowovor, is no ]iro<it" tliat they are not 

 true boulders. 



To coniplcte tlie ^^lacial pictun-, it is arisertod that a gi<^antic 

 moraine stretched across the mouth of the valley — thou<4;h, as 

 Dr. Newberry says, *' a moraine can hardly be formecl by a 

 glacier, excc})! where there are clitl's and pinnacles along its 

 com-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 contenninous with the drift of high latitudes, arc 

 absent from e([uatorial coasts. Thus avc are called ujwn 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 singidarly defective. 



2. We object to the theory because the formation contains 

 Tertiary shells. Previously to the expedition of the writer 

 across the continent in 18(37, 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 Anuizonian basin." x\.nd it was on 

 this negative evidence mainly that the distinguished naturalist 

 hazarded the conjecture that the formation was cbift. But tlie 

 banks of the Upper Amazon prove to be highly fossiliferous. 

 At the confluence of the Ambiyacu with the Maranon stands 

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

 tinga, long. 12°. The site is a level tract, about fifty feet 

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

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

 continuous Avith the Tabatinga beds and with those on the 

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

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

 contestably in situ, we discovered numerous small shells. 

 They were examined by ]\Ir. Gabb, of Philadelphia, who pub- 

 lished f the following species : — TurhoniUa mi'nuscuh, n. sp. ; 

 Neritina inipa^ Linn. ; Mesalia Ortoni^ n. sp. ; Tellina ama- 

 zonensi's, n. sp. ; Pachydon obh'quus, n. sp. ; P. tenuis, n. sp. 



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

 perienced English collector, residing at that place, to search 



• It 8eems to U3 that if " the waters of the lake were suddenly released," 

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

 alonf 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. Journ. Conch, vol. iv. p. 167. 



23* 



