192 GEOGNOSY AND GEOLOGY. 
circumstances similar to those already mentioned with respect to the 
mammoth or priscine elephant. Canines are wanting in the rhinoceros, and 
of incisors sometimes there are 3, sometimes none. There are several 
molars on each side of both jaws. Rhinocerus tichorhinus is of frequent 
occurrence ( pl. 40, figs. 14 and 15). 
Fossil elephants are very widely diffused, but most abundant in the high 
north, especially in Siberia: the ivory from this region of country enters 
largely into trade. Perfect specimens have been obtained from the ice- 
cliffs, covered with a woolly hair mixed with longer bristles. Their 
grinders are composed of vertical lamelle, of dentine, enamel, and cement ; 
and there are but two teeth, sometimes only one, on each side of the 
jaw. A molar of Klephas primigenius, or mammoth, is represented in 
pl. 40, fig. 16, from the upper surface 
The genus Mastodon, now entirely extinct, exhibits close relations to the 
elephant, having the same general structure of frame, tusks, proboscis, &c., 
but differing in the molar teeth. These, tc the number of one to four on 
each side of the jaw, exhibited two rows of mastoid or nipple-shaped 
protuberances of considerable size along the face of the tooth; these were 
sometimes united, so as to exhibit a series of transverse high ridges along 
the tooth. Some individuals possessed tusks of immense size. This genus 
is represented by several species, the existence of only one of which, on the 
continent of North America, has been satisfactorily ascertained. This 
species (Mastodon giganteus, pl. 40, fig. 19, head) is found in various 
"localities, the most celebrated being Big-bone Lick in Kentucky. It has, 
however, been found in many other States of the Union. The most perfect 
specimens exist in collections in Cambridge and Boston, as also in Phila- 
delphia, the British Museum, &c. 
Armadilloid animals, which at present are only found living in South 
America, are represented by fossil forms in Europe. Some extinct species 
of very large size have also been found in the sands near Buenos Ayres, as 
Glyptodon clavipes, six feet long (pl. 40, fig. 11%). This possessed an armor 
composed of hexagonal pieces; as also other anatomical peculiarities 
distinguishing it from its allies. 
Megatherium, found in various parts of North and South America, is 
represented, perhaps, by but a single species, M. cuvieri. Pl. 40, fig. 20°, 
is a figure of a skeleton sent to Madrid from Buenos Ayres. This animal 
was of a clumsy build, having a great similarity in the form of the skull to 
the sloth. It occupied a position in point of size between the elephant 
and the rhinoceros. It had neither incisor nor canine teeth, but 18 molars. 
Its mode of life must have been somewhat similar to that of the sloth, 
although probably not arboreal. It seems rather to have procured its food 
(twigs and leaves) by uprooting trees, which it was well capable of doing 
by means of its sharp claws, immense straight and thick broad tail, &e. 
Pl. 40, fig. 20°, is a supposed restoration of the animal. 
Mylodon was not unlike Megatherium in general character, and is 
represented by three species. A complete skeleton was found in the sands 
of the Rio de la Plata, not far from Buenos Ayres; it is about eleven feet 
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