The following characters apply especially to llamas. Dentition of adults:-incisors 1/3 canines 1/1, premolars 2/2, molars 3/2; total 32. In the upper jaw there is a compressed, sharp, pointed laniariform incisor near the hinder edge of the premaxilla, followed in the male at least by a moderate-sized, pointed, curved true canine in the anterior part of the maxilla. The isolated canine-like premolar which follows in the camels is not present. The teeth of the molar series which are in contact with each other consist of two very small premolars (the first almost rudimentary) and three broad molars, constructed generally like those of Camelus. In the lower jaw, the three incisors are long, spatulate, and procumbent; the outer ones are the smallest. Next to these is a curved, suberect canine, followed after an interval by an isolated minute and often deciduous simple conical premolar; then a contiguous series of one premolar and three molars, which differ from those of Camelus in having a small accessory column at the anterior outer edge.

The skull generally resembles that of Camelus, the relatively larger brain-cavity and orbits and less developed cranial ridges being due to its smaller size. The nasal bones are shorter and broader, and are joined by the premaxilla.

Vertebrae:

• cervical 7,

• dorsal 12,
• lumbar 7,
• sacral 4,
• caudal 15 to 20.

Ears are rather long and pointed. There is no dorsal hump. Feet are narrow, the toes being more separated than in the camels, each having a distinct plantar pad. The tail is short, and fur is long and woolly.

In essential structural characters, as well as in general appearance and habits, all the animals of this genus very closely resemble each other, so that whether they should be considered as belonging to one, two, or more species is a matter of controversy among naturalists.

The question is complicated by the circumstance of the great majority of individuals which have come under observation being either in a completely or partially domesticated state. Many are also descended from ancestors which have previously been domesticated; a state which tends to produce a certain amount of variation from the original type. It has, however, lost much of its importance since the doctrine of the distinct origin of species has been generally abandoned. The four forms commonly distinguished by the inhabitants of South America are recognized by some naturalists as distinct species, and have had specific designations attached to them, though usually with expressions of doubt, and with great difficulties in defining their distinctive characteristics.

These are:

• the llama, Auchenia glama (Linn.), or Lama peruana (Tiedemann);

• the alpaca, A. pacos (Linn.);
• the guanaco or huanaco, A. huonaeus (Molina); and
• the vicuña, A. vicugna (Molina), or A. vicuiena, (Cuv.).

The llama and alpaca are only known in the domestic state, and are variable in size and colour, being often white, black, or piebald. The guanaco and vicuña are wild and endangered, and of a nearly uniform light-brown colour, passing into white below. They certainly differ from each other, the vicuña being smaller, more slender in its proportions, and having a shorter head than the guanaco. The vicuña lives in herds on the bleak and elevated parts of the mountain range bordering the region of perpetual snow, amidst rocks and precipices, occurring in various suitable localities throughout Peru, in the southern part of Ecuador, and as far south as the middle of Bolivia. Its manners very much resemble those of the chamois of the European Alps; it is as vigilant, wild, and timid. The wool is extremely delicate and soft, and highly valued for the purposes of weaving, but the quantity which each animal produces is minimal.