84 



GEOLOGY. 



this order is reversed, there being two tusk-like incisors in the lower 

 jaw, and none in the upper. 



In another extinct form, the Mastodon (see Fig. ]), the incisors 

 are usually developed in the upper jaw, and form tusks as in the 

 Elephants ; but sometimes there are both upper and lower incisors, 

 and both are tusk-like (see Fig. 4). All these animals had, like the 

 living Elephants, a cylindrical trunk or proboscis (snout) with a 

 prehensile extremity, serving to gather and convey the food to the 

 mouth. The soles of the feet, supporting the weight of the body, 

 are provided with a thick pad covered by the skin, and in this the 

 five toes are enclosed and concealed in the living animal, but the 

 nails of the toes can generally be seen.* 



Only two living species of Elephants are known ; one, the Asiatic 

 Elephant, confined to India, Ceylon, &c. ; the other, the African 

 Elephant, peculiar to the continent of Africa. These are well-marked 

 species, not only by their external characters, but also by their grind- 

 ing teeth (see Figs. 5 and 6). These teeth in the Elephants are 

 composed of strong enamelled plates encased in a thick setting of 

 cement — the plates varying in number and in pattern in the diffe- 

 rent species. Thus the African Elephant has fewer plates of enamel 

 in each tooth, and these on the grinding surface are worn down to a 

 lozenge-shaped pattern (Fig. 6) ; the Indian Elephant having many 

 plates, closely folded together and finely crimped at their edges 

 (Fig. 5). The teeth of the larger number of fossil Elephants 

 resemble those of existing species, but in some of the earlier forms 

 they approach more nearly in character those of the Mastodon. 



The Mastodons were Elephants with the grinding teeth less complex 

 in structure, and adapted for bruising coarser vegetable substances. 

 The grinding surface of the molars, instead of being cleft into numerous 

 thin plates, was divided into wedge-shaped transverse ridges, and the 

 summits of these were subdivided into smaller cones, more or less 

 resembling the teats of a cow, whence the generic name is derived. 



In Wall-case 23, on the left-hand side of the door, are placed the 

 fossil remains of the Dinotherium, a hoofed quadruped, supposed to 

 have been intermediate between the Tapir and the Mastodon, the 

 most perfect remains of which have been found in the Miocene 

 Tertiary formation of Epplesheim, Hesse-Darmstadt, Germany, while 

 others have been found in France, Switzerland, and Perim Island, 

 Gulf of Cambay. The original skull of Dinotherium, described by 

 Dr. Kaup, together with a reproduction of the lower jaw, are placed on 

 a separate stand (marked B on plan) in this gallery. {See p. 16, Fig. 3.) 



The entire skeleton of the Mastodon from Ohio stands facing the 

 entrance to the gallery. (See Vignette Title-page.) Near it are 

 placed the head and lower jaw of the South-American Mastodon from 

 <3hile (Mastodon Andium-f) ; and on another stand is exhibited the 



* The external form of the feet can still be seen in the fossil Mammoth from 

 •Siberia, preserved at St. Petersburg. 



f Marked (C) on plan and placed on the North side of this ( Gfallery next Table- 

 •case 23. 



