420 ON THK FOSSIL BONES OF PACHYDERMATOUS QUADRUPEDS. 



This parti} 7 happened to our rhinoceros ; he had already lost his first 

 molar tooth on each side, and the alveoli were nearly effaced ; he had 

 worn the next molar tooth down to the roots, and he had even already 

 lost on one side one of the stumps of the root, whilst the stumps on 

 the other side still remained, (m, plate 40, fig. 4). 



But if this rhinoceros had lost molar teeth with age, he had not 

 gained incisors ; that does not happen more to him than to other animals 

 which become old. The two small intermediate incisors of the lower 

 jaw (?z, n, plate 40, fig. 4) exist from youth, as is seen in the head 

 given to the cabinet by M. Adrien Camper, and better still by the ex- 

 tremity of the lower jaw of a very young animal, of which a drawing 

 was made by his father, and published in the Acts of Petersburg for 

 1777, plate ix, fig. 3, copied (plate 42, fig. 5) and reproduced here, 

 from nature, plate 43, fig. 2 ; but they always remain concealed under 

 the gum ; and that was the reason why Meckel had not seen them in 

 the living animal, whilst they are manifest in the skeleton. M. Thomas, 

 a surgeon of London, who has published some anatomical observations 

 on the one-horned rhinoceros, also found these small teeth in the 

 skeleton of an animal four years old. 



But what no one to my knowledge has yet published is this, that 

 the rhinoceros has, during a certain time of its life, two similar 

 incisives in the upper jaw ; only there they are outside the large ones, 

 whilst in the lower jaw they are between the large ones. This might 

 be already inferred from the drawing of the intermaxillary bone of the 

 very young rhinoceros, given by the elder Camper (in the Acta Petrop. 

 t. i, plate ix, fig. 2), and of which I reproduced the subject more entire, 

 plate 43, fig. 3. At first I even thought that this character necessarily 

 indicated another species ; but on examining the drawings of the 

 anatomy of our rhinoceros, made with the greatest care by Marechal, 

 under the eyes of Vicq-dAzyr and Mertrud, I recognized the figure 

 of a very small tooth outside the upper great incisive of the right side ; 

 and I saw in the explanation accompanying this drawing, and which 

 is from the hand of Vicq-dAzyr, that there was on this side a small 

 tooth, which was wanting on the other side : on recurring to the skeleton, 

 I found there on one side a remnant of an alveolus ; but the tooth, 

 already too much rooted up, was lost at the time of maceration ; on the 

 other side, the alveolus itself was effaced. 



The number of the teeth being thus well ascertained, we may now 

 pass on to their description. 



In order clearly to understand the teeth of herbivorous animals, it is 

 not sufficient to see them, as those of carnivorous animals, at a single 

 period of life ; these teeth constantly wearing, the crown also changes 

 continually, and the naturalist must follow them, from the time they 

 pierce the gum, till they fall out of the mouth. 



However, it is not always necessary for the purpose, to have at one's 

 disposal individuals of all ages, As the front teeth appear soonest, 

 they are also worn soonest ; and one may often follow in a single 

 jaw all the degrees of detrition, going from the posterior to the anterior 

 teeth. 



Here then is what is observed regarding the teeth of the one- 

 horned rhinoceros of India, and first to the upper teeth, plate 40, 



