Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/762

 738 L L A L L A tlieir own wriggling tail. They are of a fierce disposition, frequently fighting among themselves; but house-geckos readily become habituated to the presence of man ; ac customed to be fed at a certain time with rice, these little lizards will punctually make their appearance, and fearlessly take the proffered food. Another peculiarity of geckos is that they, or at least some genera, are endowed with a voice. The large Gecko yuttatus and G. monarchiis of the East Indies utter a shrill cry, sounding like &quot; tokee &quot; or &quot; tok.&quot; The common species found in houses in the south of Europe are a species of Hemidactylus (If. verrucidatus) and Tarentola, the terrentola of the Italians. All geckos seem to be oviparous. (A. c, G.) LLAMA, sometimes spelt Lama, a word by which the Peruvians designated one of a small group of closely allied animals, which, before the Spanish conquest of America, were the only domesticated hoofed mammals of the country, being kept, not only for their value as beasts of burden, but also for their flesh, hides, and wool, in fact, supplying in the domestic economy of the people the place of the horse, the ox, the goat, and the sheep of the Old World. The word is now sometimes restricted to one particular species or variety of the group, and sometimes used in a generic sense to cover the whole. Although they were often compared by early writers to sheep, and spoken of as such, their affinity to the camel was very soon perceived, and they were included in the genus Camelus in the Systema Naturx of Liiirueus. They were, however, separated by Cuvier in 1800 under the name of Lama, changed by Illiger in 1811 to Auchenia (in allusion to the great length of neck, av^-r jv), a term afterwards adopted by Cuvier, and almost universally accepted by systematic zoologists, although there has been of late a disposition to revive the earlier name. The animals of the genus Auchenia or Lama are, with the two species of true camels (to which the generic term Camelus is now restricted), the sole existing representatives of a very distinct section of the &quot; artiodactyle &quot; or even- FIG. 1. Llama (from an animal living in the Gardens of the Zoological Society of London). toed ungulates, called Tylopoda, or &quot; boss-footed,&quot; from the peculiar bosses or cushions placed on the under surface of their feet, and on which they tread. This section thus consists of a single family, the Camelidee., the other sec tions of the same great division being the Suina or pigs, the Trayulina or chevrotains, and the Pecora or true ruminants, to each of which the Tylopoda have more or less affinity, standing in some respects in a central position between them, borrowing as it were some characters from each, but in others showing great special modifications not found in any of the other sections. Until within the last few years the existence of two genera having so very much in common as the camels and the llamas, and yet so completely isolated geographically, had not received any satisfactory explanation, for the old idea that they in some way &quot; represented &quot; each other in the two hemispheres of the world was a mere fancy without philosophical basis. The discoveries made mostly within the past ten years of a vast and previously un suspected extinct fauna of the American continent of the Tertiary period, as interpreted by the able paleontologists Leidy, Cope, and Marsh, has thrown a flood of light upon the early history of this family, and upon its relations to other mammals. It is now known that llamas at one time were not confined to the part of the continent south of the Isthmus of Panama, as at the present day, for their remains have been abundantly found in the Pleistocene deposits of the region of the Kocky Mountains, and in Central America, some attaining a much larger size than those now existing. There have also been found in the same regions many camel-like animals exhibiting different generic modifications, and, what is more interesting, a gradual series of changes, coinciding with the antiquity of the deposits in which they are found, have been traced from the thoroughly differentiated species of the modern epoch down through the Pliocene to the early Miocene beds, where, their characters having become by degrees more generalized, they have lost all that especially distinguishes them as Camelidge, and are merged into forms common to the anecstral type of all the other sections of the Artio- dactyles. Hitherto none of these annectant forms have been found in any of the fossiliferous strata of the Old World ; it may therefore be fairly surmised (according to the evidence at present before us) that America was the original home of the Tylopoda, and that the true camels have passed over into the Old World, probably by way of the north of Asia, where we have every reason to believe there was formerly a free communication between the con tinents, and then, gradually driven southward, perhaps by changes of climate, having become isolated, have undergone some further special modifications ; while those members of the family that remained in their original birthplace have become, through causes not clearly understood, restricted solely to the southern or most distant part of the continent. There are few groups of mammals of which the palasontological history has been so satisfactorily demonstrated as the one of which we are treating. 1 The special characters which the llamas and camels have in common, and the combination of which distinguishes them from the rest of the Artiodactyles, are as follows. The premaxilla? have the full number of incisor teeth in the young state, and the outermost is persistent through, life, an isolated laniariform tooth. The canines are present in both jaws, and those of the mandible are dif ferentiated from the long, procumbent, and spatulate incisors, being suberect and pointed. The crowns of the true molars belong to the crescentic or &quot; selenodont &quot; type, and are very long or &quot; hypsodont&quot;; but one or more of the anterior premolars is usually detached from the series, and of simple pointed form. The hinder part of the body is much contracted, and the femur long and vertically placed, so that the knee-joint is lower in position, and the thigh alto gether more detached from the abdomen than in most quadrupedal mammals. The limbs are long, but with only two digits (the third and fourth) developed on each, no traces of any of the others being present. The trapezoid and magnum of the carpus, and the cuboid and navicular of the tarsus are distinct. The two metapodal bones of each limb are confluent for the greater part of tlieir length, though 1 See especially E. D. Cope, in Wheeler s Report nf (he Survey West of the lOOth Meridian, iv. pt. 2, pp. 325-46, 1877.