34 



DESCRIPTION OF THE PLATES. 



upper jaw, \ nat. size, of a Colt of two 

 years. Fig. 6. The dentition of a Colt of 

 three years, from the inner side of the 

 upper jaw, \ nat. size. Rousseau. Fig. 



7 . The incisors and canine of the left side 

 of the lower jaw of a Colt of four years, 

 ^ nat. size. The third permanent inci- 

 sor, i 3, has not yet displaced its decidu- 

 ous predecessor, d, i 3. Rousseau. Fig. 



8. The incisors of the right side of the 

 upper jaw of a Horse of five years, shew- 

 ing the mark a, long and deep in all, and 

 irregular on the inside in the outer incisor, 

 i 3. Fig. 9. The upper incisors and ca- 

 nine of the right side of a Horse of six 

 years, shewing the mark faint in the first 

 and second incisors ; but the inflected 

 margins and point of the canines, c, are 

 still sharp. Fig. 10. The upper incisors 

 and canine of the right side of an aged 

 Horse, about sixteen years. The cavity 

 of the mark is obliterated ; the dark co- 

 loured osteo-dentine, and some remains 

 of cement in the outer incisor, indicate 

 their place ; the margins and point of the 

 canine are rounded off. Fig. 1 1 . Longi- 

 tudinal section of an incisor showing the 

 depth of the vertical fold of enamel a, and 

 the cement at its bottom a} ; e, is the outer 

 enamel and c, the outer cement. Rous- 

 seau. 



PLATE 137. 



A section of part of the crown of a molar of 

 ;t Horse, showing a dentine ; b, enamel ; 

 c, cement, in which are many vascular 

 canals, v v. Magnified 150 linear diame- 

 ters. Original. 



PLATE 138. 



Fig. 1. Reduced view of the skull of the 

 extinct hornless Rhinoceros, (Acerothe- 

 rium incisivum), Kaup. Fig. 2. Reduced 



view of the skull of the two horned Rhi- 

 noceros (Rhinoceros bicornis). Cuvier. 

 Fig. 3. Grinding surface of molar series, 

 right side upper jaw, \ nat. size, of the one- 

 horned Rhinoceros (Rh. indicus), Cuvier. 

 Fig. 4. Grinding surface of first true molar 

 of the Java Rhinoceros (Rh. sondaicus). 

 Fig. 5. Ditto of the Rhinoceros bicornis. 

 Fig. 6. Ditto of the Rhinoceros tichorhinus. 

 Fig. 7. Ditto of the Rh. leptorhinus. Fig. 

 8. Germ of a molar of Rh. tichorhinus. 

 All the above figures of upper molars are 

 reduced \ in size : o, outer side ; o 1 lon- 

 gitudinal ridge ; i i, inner lobes ; b, valley 

 dividing the inner lobes ; e, its termina- 

 tion which becomes wholly, or partially, 

 or not at all insulated, according to the 

 species ; c , valley entering from outer 

 side (it is marked e, in fig. 4). /. Pro- 

 montary projecting into or crossing valley 

 b. Fig. 9. Grinding surface of two mo- 

 lars of the lower jaw, -| nat. size, of Rhin. 

 indicus. Fig. 10. Four premolars, leftside 

 lower jaw, with symphysis in outline of 

 the Rhin. tichorhinus, £ nat. size. Fig. 

 11. Four premolars left side, lower jaw, 

 and symphysis of the Rhin. leptorhinus ; 

 \ nat. size. Fig. 12 (printed 1). Out- 

 line of the right intermaxillary bone of 

 the two-horned Rhinoceros of Sumatra. 

 (Rh. Sumatranus), ^ nat. size; i 1, first 

 incisor; i 2, second incisor. Fig. 13. 

 Portion of left superior maxillary bone of 

 a young Rhinoceros Indicus showing c ru- 

 diment of a canine, and p 1 the hidden 

 crown, exposed from without, of the first 

 premolar. Fig. 14. Symphysis and part 

 of lower jaw of a very young Rhinoceros 

 bicornis, \ nat. size, showing the germs 

 of four incisors (i 1 and i 2 on each side) ; 

 d 1 , first deciduous molar ; d 2, second 

 deciduous molar. Fig. 15. Symphysis 

 of lower jaw of a half-grown Rhinoceros 



