166 NATURAL HISTORY MISCELLANY. 
fossil shells exposed in the fine section made by the Ambiyacu just before 
t reaches the Marafion. These shells were examined by Gabb, who 
explore for other localities, being sure they would be found. He soon re- 
rted a similar deposit thirty miles below Pebas on the south side of the 
Marañon, about one hundred and twenty miles west of Tabatinga, where 
spe 
larger kinds. Out of half a bushel of specimens which he sent me, this 
is the result arrived at by our eminent paleontologist, Mr. Conrad. Not 
one species was found in the whole collection which is now living; indi- 
extinct, belonging to genera only three of which are now represented. 
st numerous species seems to be the iene (Pachydon) obli- 
quus. In the whole collection there is but one land shell (Bulimus), and 
ip one decidedly fresh-water species (Hemisinus). The great majority 
belong to a genus which was especially abundant in the early Tertiary, 
and lived in brackish water. This agrees perfectly with my theory of the 
e 
ereated the Orinoco and Paraguay, it was gradually freshened by the in- 
flux of the fresh-water streams from the surrounding highlands, and 
gradually emptied into the Atlantic by the co ontinued rise of the Andes. 
The fossils were found in the heart of the valley interstratified with the 
colored laminated clays which I had traced from Curary on the Rio Napo 
down to the Lower Amazon, and which Agassiz affirms is a glacial de- 
moving over the whole plain. 'This is mere assertion, for he found not 
one positive evidence. Besides, there are strong biological and physical 
sil 
the least abrasion; a glacier would have ground them to powder. Con- 
rad says they must have lived and died in the vicinity of the spot where 
they now occur so abundantly.—JAMES Orton, Nov. 15, 1870. 
Leap Mines or Missouri. — Mr. G. C. Broadhead read a paper before 
the St. Louis Academy of Science € October, entitled ** Notes on the 
Geology of Cole County, Missouri. He mentions that the Magnesian 
limestone series, which include the rich mineral deposits of Missouri, 
occur in Cole County, and that the rich Galena lead mines are in the lower 
beds of the second Magnesian limestone. At Fowler's mines he noticed 
, zinc, - heavy spar; the latter in very clear amber-colored crystals 
and in blue lamellar forms 
Marks OF ANCIENT GLACIERS ON THE PacrFic Coast.— Dr. Robert 
Brown dissents from the theory of an entire absence of glacial remains 
proper on the Pacific slope of the Rocky Mountains, stating that the 
