all the twenty-four species of Opossums known from the New World are found within its limits. The peculiarly modified Water-opossum (Chironectes) occurs all over its area, but also extends into the Central-American Subregion.

Among the Edentates the Sloths are the most characteristic inhabitants of its forests. But two peculiar genera of Armadilloes (Xenurus and Priodon) are confined to this Sub-region, and several other species of this group occur there. All three genera of Ant-eaters are also here met with.

Rodents are very abundant in this Sub-region, but, with the exception of Squirrels (Sciurus), Vesper-mice (Hesperomys), Pouched mice (Heteromys), and a single Hare (Lepus), they all belong to the Hystricomorphine group, which is so highly developed in the Neotropical Region.

The Guiano-Brazilian Sub-region is also the special home of the Phyllostomine bats. Out of a total of about sixtyfive species of this family forty-four are found in this Sub-region, and the greater number of them are confined to it. Such, too, is the case with the Platyrrhine monkeys. The Marmosets (Hapalide) would be also unknown outside the limits of the Sub-region had not a single species, as already mentioned, overstepped the northern boundary at Panama. The Capuchins (Cebida), numbering more than sixty species and belonging to ten genera, are likewise abundant, and are found elsewhere only in the Central-American Sub-region.

The following table shows at a glance the numbers of (1) the "Endemic" genera of this Sub-region, i.e. those not found beyond its limits; (2) the "Neotropical" genera, i.e.

those confined within the limits of the whole Region; (3) the "American" genera, i.e. those occurring in other parts of the New World, but not beyond; and (4) the “Cosmopolitan," i.e. those of general distribution:

The Patagonian Sub-region may be most conveniently taken to begin on the south side of the bay of Guyaquil, and to extend thence southwards, embracing the whole western slope of the Andes of Ecuador and Peru. In Bolivia it widens out and includes the high plateau of Titicaca, extending thence over the whole of the Argentine Republic, Chili, and Patagonia.

The most characteristic form of the mammals of this Sub-region is the Lama, which, with its allies, constitutes the genus Lama. Four forms, usually regarded as distinct species, are recognised by naturalists. Of these two, the Lama (L. peruana) and the Alpaca (L. pacos) are only met with in a domestic state, and are very variable in size and colour. Of the other two, which are met with wild, the Guanaco (L. huanacos) has the most

7500

30

44

10

11

95

Total.

extensive distribution, ranging from the highlands of Ecuador and Peru, along the Andes, to the open plains of Patagonia; while the Vicugna (L. vicugna), which is a somewhat smaller animal, is found only in Ecuador, Peru, and Bolivia.

In addition to the Lamas, this Sub-region possesses a species of thickly haired mountain Tapir, differing from the lowland forms, and two or three peculiar Deer, of the sub-genus Furcifer, which are likewise densely furred. A third diminutive deer found in Chili is distinguished from Cariacus, the ordinary American form of deer, by anatomical characters, and belongs to a special genus, Pudua. A second species of this form (P. mephistopheles) from the highlands of Ecuador has lately been described by Mr. De Winton.

The Rodents of the Patagonian Sub-region almost all belong to the Hystricomorphine section of the Order. Amongst them are the Chinchillas (Chinchilla and Lagidium), noted for their delicate fur, the Viscacha (Lagostomus), and the Patagonian Cavy (Dolichotis). Out of the eighteen genera of this division known to occur in the Patagonian Sub-region, ten are restricted to it.

Of the carnivorous Mammals of this Sub-region, one of the most interesting is the Spectacled Bear of the Andes (Ursus oratus), which affords an instance of that rare phenomenon in nature "discontinuous distribution," the nearest allied species of bear (the black bear of North America) only coming as far south as Mexico. The presence of a bear in the Andes can only be explained by the supposition that the ancestral form migrated southwards along the line of the Cordilleras, but has died out in the intermediate district. The Bats of the Patagonian

Sub-region present but few features of interest; they are, with one exception, all of genera found also in the GuianoBrazilian Sub-region.

As might have been expected from the dearth of forests and the generally severe climate, the American monkeys and marmosets are entirely unrepresented in the Patagonian Sub-region. On the other hand, at least two small species of Opossum (Didelphys and Dromiciops) occur in Chili, and a very remarkable form of Armadillo (Chlamydophorus) is peculiar to Argentina and the high plateau of Bolivia.

The following list of the mammal genera of the Patagonian Sub-region is constructed on the same plan as that of the preceding tables:

SECTION VIII.-THE PAST HISTORY OF THE

NEOTROPICAL MAMMAL-FAUNA

During the last few years our knowledge of the extinct mammals of the Neotropical Region has been enormously increased by the discoveries of the paleontologists of the Argentine Republic, more particularly by the labours of

Burmeister, Moreno, and Ameghino. A few words about this branch of the subject may be added.

The oldest formation containing well-preserved remains of mammals yet investigated is in the neighbourhood of Santa Cruz, in Southern Patagonia, where the deposits are about 200 feet in thickness. The exact age of the Santa Cruz beds it is very difficult to determine, but the best authorities consider that they cannot be of earlier date than the Upper Eocene or Oligocene of Europe. Following these in point of time, are the so-called "Patagonian' beds of Patagonia and Uruguay, which are probably of Miocene age. The "Araucanian" formation of Ameghino, which is well developed at Monte Hermoso, near Bahia Blanca, in Southern Argentina, seems to correspond approximately with the older European Pliocene. Finally, the later Pliocene is apparently represented by the "Pampas" formation of Argentina and Uruguay. Our knowledge of the extinct mammal-faunas of these beds is mainly due to the efforts of the Argentine palæontologists just mentioned, but a clear résumé of the work done will be found in a recent number of the Geological Magazine (12).

In the "Santa Cruz" beds have been found remains of about 120 genera of mammals referable to the following groups :

Marsupials.
Edentates.

Perissodactyles.
Toxodonts.

Rodents.
Monkeys.

Among the Marsupials the most prominent forms in this formation are the Opossums (Didelphyida), which are still found all over America, and in Tertiary times appear to have been distributed nearly all over the northern hemisphere. But accompanying these are other forms of the