15 
fish-teeth. These shales are followed by limestone, with 
layers of cherty nodules; and lower down, these limestones 
become highly fossiliferous, yielding very perfect and beauti- 
ful specimens of Productus, Strophalosia, ete., all of which are 
generally silicified, and may be obtained in great perfection, 
where the water has worn away their calcareous matrix. The 
lower layers of these limestone beds are quite soft, and the 
upper ones much harder. At many points along the bank, 
the floods have eroded these lower layers, leaving the upper 
ones oyer-hanging, sometimes so as to form perfect grottoes, 
‘from the roofs of which project beautiful specimens of Pro- 
ductus, with their long spines unbroken, and delicate 
Strophalosias, hanging almost by a thread of rock, and ready 
to drop at a touch into the delighted collector’s hand. 
All the species obtained,—brachiopods, lamellibranchs, 
gasteropods, and cephalopods (of which there is only an 
Orthoceras, no Nautili or Goniatites)—bear a singularly close 
resemblance to the familiar Carboniferous species of the 
northern hemisphere. Further down, these rocks become 
covered up by the Tertiary beds of the Amazon valley; but 
they appear again, with the same fossils, in corresponding 
positions on the northern side of the great stream, on the Rio 
Trom betas. 
An extended area of Carboniferous deposits, for the most 
part undisturbed, is thus traceable through this portion of 
the basin of the Amazonas; while eastward of the Tapajos no 
indication thereof has been found. On the southern side, 
however, of the great Brazilian plateau, rocks of the same age 
have been recognized. 
In the more eastern portion of the Amazon yalley, a con- 
siderable Devonian area has been proved to exist. These 
rocks contain many species of characteristic Devonian 
brachiopods, Chonetes, Spirifer, Vitulina, ete. Two fine trilo- 
bites have been obtained here, a Lichas and a Homalonotus.* 
Prof. Hartt also gave an account of his researches among 
the antiquities of the country, and discussed their relations 
* Most of these are to be described in the Annals, Vol. XI. 
