We here have the puzzle that so frequently occurs in the case of musquitoes--on the blood of what animals do these insects commonly feed?
The guanaco is nearly the only warm-blooded quadruped, and it is found in quite inconsiderable numbers compared with the multitude of flies.
The geology of Patagonia is interesting.

Differently from Europe, where the tertiary formations appear to have accumulated in bays, here along hundreds of miles of coast we have one great deposit, including many tertiary shells, all apparently extinct.

The most common shell is a massive gigantic oyster, sometimes even a foot in diameter.

These beds are covered by others of a peculiar soft white stone, including much gypsum, and resembling chalk, but really of a pumiceous nature.

It is highly remarkable, from being composed, to at least one-tenth part of its bulk, of Infusoria: Professor Ehrenberg has already ascertained in it thirty oceanic forms.