In America there is also but one species of wild sheep, though it has also a variety. This is the Bighorn of the Rocky Mountains, lately much spoken of by prairie travellers and fur-hunters. It is not known in tropical North America, nor does its range extend to the Andes of the south; but it is found to the west, in the mountains of California, in a variety called the Californian sheep. The bighorn is extremely like the Asiatic argali, and was for a long time regarded as identical with the latter; but this was an error. It is now ascertained that not only is the American animal of another species, but also that there are several distinct species of the argali itself in the different ranges of Asiatic mountains. Africa has its wild sheep, but only in its northern parts. This is the Aoudad, which dwells in the mountains of Barbary. Asia appears to be the head-quarters of the wild sheep. One species is found in Armenia, and another in the Caucasus. Siberia has an argali, that appears altogether to differ from the argali of the Himalayas. Again, in the Himalayan Mountains themselves, there is one species which ranges north only as far as Thibet; while on the Thibetian plateaux, as far as the Altai Mountains, there is another, if not two other species, quite distinct from the latter. It has been observed by competent travellers, that these Thibetian argalis bear a very strong resemblance to the different breeds of tame sheep found in the same regions; from which it may be reasonably inferred that the domesticated varieties of different countries have sprung from several wild species, instead of being all descended from one common origin. CHAPTER TWENTY. GOATS.