diag List of Mammalian remains found in the Buenos Ayres district,¹ and purchased by the British Museum²

Ord. Edentata

Gen. Megatherium—remains of at least three if not four individuals. The bones which we possess vary much in size, and yet the smallest do not show any indications of immaturity—possibly the sexes differed in size.

Mylodon robustus—remains of one individual

Genus Glyptodon, remains of at least three distinct species— cannot say whether there be more than one individual of each.

Ord. Pachydermata

Mastodon audium remains of three individuals

Macrauchenia—a ramus of a lower jaw, with the molar teeth, supposed to belong to this animal—the form of the jaw and teeth greatly resembles that of a Rhinoceros

Toxodon—a complete lower jaw, with many of the teeth,—supposed to differ from the T. platensis—, and anterior part of the upper jaw, probably of a different individual— this fragment is in a different condition to the lower jaw, and was imbedded in a blackish earth containing minute particles of iron pyrites(?) like gold dust, a leg bone of a glyptodon & some of the Mastodon remains present the same conditions Ord.

Carnivora

Machairodus Kaup— Great portion of the skull

& a nearly perfect lower

Smilodon, & formerly jaw of the same individual— Hyæna of Lund

I feel no doubt that these parts belonged to an animal specifically

identical with one found in the Brazilian caverns—

As far as we know, however, the extinct species are generally distinct

in the two districts, Brazil & La Plata, or at least those found in

the latter quarter are rare in Brazil & vice versa. We have a tooth

of a Megatherium from the Brazil caverns but in those caves I have

found no Mylodon remains, a nearly allied animal the Scelidotherium

was there abundant, judging from the remains—which belong to

2 or 3 species. Our Glyptodons from Brazil are distinct from those

of Buenos-Ayres— There must be at least 6 or 7 species of Glyptodon,ramme

My dear Darwin

I need scarcely say if there are any other points I can help you in, I shall with pleasure do it.

Believe me faithfully yours | Geo. R. Waterhouse British Museum

Monday morning