C. F. Hartt—Tertiary Basin of the Marafion. 57 
Mr. Steere has made very extensive collections of the fossils 
of the Pebas locality and vicinity, and they will probably 
afford some new species. When these collections with their 
accompanying lithological specimens shall have been studied, 
we shall have more details relative to the character of the beds 
tof. Agassiz could have seen the blue clays in the neighbor- 
hood of Tabatinga, for he makes no mention of the lignites 
Which occur in them, and it also seems to me doubtful whether 
variegated clays, but in an older and distinct underlying forma- 
te quite unlike the ordinary more recent variegated clays of 
ing the age of the lower series, leaving the question of the age of 
the superficial clays undecided. They certainly afford no proof 
them with the superficial clays of the Lower Amazonas, for my 
,Xperience with these deposits has satisfied me, that, how simi- 
: er these beds may be in different localities, they may 
