926 



TEETH. 



Ungulates ; it is not a mere miniature of the 

 great molars of the mature animal, but re- 

 tains, agreeably with the period of life at 

 which it^is developed, a character much more 

 nearly approaching that of the ordinary Pa- 

 chydermal molar, manifesting the adherence 

 to the more general type by the minor com- 

 plexity of the crown, and by the form and 

 relative size of the fangs. In the transverse 

 divisions of the crown we perceive the affinity 

 to the Tapiroid type, the different links con- 

 necting which with the typical elephants are 

 supplied by the extinct Lophiodons, Dino- 

 theriums, and Mastodons. The sub-division 

 of the summits of the primary plates recalls 

 the character of the molars, especially the 

 smaller ones, of the Phacochere in the Hog- 

 tribe. As the elephant advances in age the 

 molars rapidly acquire their more special and 

 complex character. 



The first molars are completely in place, 

 and in full use at three months, and are shed 

 when the elephant is about two years old. 



The sudden increase and rapid develop- 

 ment of the second molar may account for the 

 non-existence of any vertical successor to the 

 former tooth, or " premolar," in the elephant. 

 The eight or nine plates of the crown are 

 formed "in the closed alveolus, behind the 

 first molar by the time this cuts the gum, and 

 they are united with the body of the tooth, 

 and most of them in use, when the first 

 molar is shed. 



The average length of the second molar is 

 two inches and a half; ranging from two 

 inches to two inches and nine lines. The 

 greatest breadth, which is behind the middle 

 of the tooth, is from one inch to one inch 

 three lines. There are two roots : the cavity 

 of the small anterior one expands in the 

 crown, and is continued into that of the three 

 anterior plates. The thicker root supports 

 the rest of the tooth. The second molar is 

 worn out and shed before the beginning of 

 the sixth year. 



The third molar has the crown divided into 

 from eleven to thirteen plates ; it averages 

 four inches in length, and two inches in 

 breadth, and has a small anterior, and a very 

 large posterior root ; it begins to appear 

 above the gum about the end of the second 

 year, is in its most complete state and ^exten- 

 sive use during the fifth year, and is worn out 

 and shed in the ninth year. The last rem- 

 nant of the third molar is shown at m. 3, 

 fig. 592. 



It is probable that the three teeth above de- 

 scribed are homologous with the deciduous mo- 

 lars, rf.2, rf.3, and rf.4. in the Hyrax and horse. 



The fourth molar presents a marked supe- 

 riority of size over the third, and a somewhat 

 different form : the anterior angle is more 

 obliquely abraded, giving a pentagonal figure 

 to the tooth in the upper jaw (fig. 592. m. 4). 

 The number of plates in the crown of this 

 tooth is fifteen or sixteen : its length between 

 seven and eight inches ; its breadth three 

 inches. It has an anterior simple ami slender 

 root supporting the three first plates ; a 



second of larger size and bifid, supporting the 

 four next plates ; and a large contracting base 

 for the remainder. The fore-part of the 

 grinding surface of this tooth begins to pro- 

 trude through the gum at the sixth year : the 

 tooth is worn away, and its last remnant shed, 

 about the twentieth or twenty-fifth year. It 

 may be regarded as the homologue of the first 

 true molar of ordinary Pachyderms (in. 1). 



The fifth molar, with a crown of from 

 seventeen to twenty plates, measures between 

 nine and ten inches in length, and about 

 three inches and a half in breadth. The 

 second root is more distinctly separated from 

 the first simple root than from the large mass 

 behind. It begins to appear above the gum 

 about the twentieth year : its duration has 

 not been ascertained by observation ; but it 

 probably is not shed before the sixtieth year. 



The sixth molar appears to be the last, and 

 has from twenty-two to twenty-seven plates ; 

 its length, or antero-posterior extent, following 

 the curvature, is from twelve to fifteen inches : 

 the breadth of the grinding surface rarely 

 exceeds three inches and a half. 



The reproductive power of the matrix in 

 some cases surpasses that of the formative 

 development of the cavity for lodging the 

 tooth, and the last lamella? are obliged to be 

 folded from behind forwards upon the side of 

 the tooth. Fig. 99, p. 233. of my " History of 

 British Fossil Mammals," shows this condition 

 in the last lower molar of the Mammoth. 



One may reasonably conjecture that the 

 sixth molar of the Indian elephant, if it make 

 its appearance about the fiftieth year, would, 

 from its superior depth and length, continue 

 to do the work of mastication until the pon- 

 derous Pachyderm had passed the century of 

 its existence. 



Mr. Corse has figured the sixth molar, 

 (which he calls the seventh or eighth,) with 

 twenty-three plates, in tab. x. of his Memoir, 

 and a small cavity, c, is marked as an in- 

 cipient alveolus for a succeeding grinder. 

 Had it actually been such, it might have been 

 expected to contain some calcified portions 

 of the anterior plates of such succeeding 

 grinder. 



The molar teeth, in all the species of 

 elephant, succeed each other from behind 

 forwards, moving, not in a right line, but in 

 the arc of a circle, shown by the curved line 

 in fig. 592. The position of the growing 

 tooth in the closed alveolus (ni. 5) is almost 

 at right angles with that in use, the grinding 

 surface being at first directed backwards in 

 the upper jaw, and forwards in the lower jaw, 

 and brought, by the revolving course, into a 

 horizontal line in both jaws, so that they 

 oppose each other, when developed for use. 

 The imaginary pivot on which the grinders 

 revolve is next their root in the upper jaw, 

 and is next the grinding surface in the lower 

 jaw ; in both, towards the frontal surface of 

 the skull. Viewing both upper and lower 

 molars as one complex whole, subject to the 

 same revolving movement, the section dividing 

 such whole into upper and lower portion runs 



