542 UNGULATES. 



year the roots begin to be developed from the base of the crown 

 of the last molars, having previously been added to those of the 

 precedent teeth. 



In the Calf, according to M. Rousseau,(l) the first deciduous 

 incisor and the first deciduous molar both cut the gum a few days 

 after birth : the second incisor and the second and third molars 

 between the fifth and tenth days : the third incisor between the 

 fifteenth and twentieth days, and the deciduous canine, which, 

 with Bojanus and Cuvier, he terms the fourth incisor, a few 

 days later. The second dentition is commenced, as in the Sheep, 

 by the eruption of the first true molar, between the fourth and 

 sixth month after birth : the first or median permanent incisor 

 and the second true molar appear between the fifteenth and 

 twenty-second month : and about the latter period the first 

 premolar pushes out the first deciduous molar. The second 

 premolar and the second incisor appear between the twenty-eighth 

 and thirty-second months. The third premolar and the third 

 incisor appear between the thirty-eighth and the forty-eighth month. 

 The last true molar cuts the gum between the forty-fourth and 

 the fifty- second month. The permanent canines (fourth incisors of 

 M. Rousseau) are the last to appear, as in the Sheep, but at an 

 earlier period, according to that Author, viz., before the Ox has 

 attained its fifth year. 



The birth and growth of a young Giraffe at the Zoological 

 Gardens of London have enabled me to make the following 

 observations on the course of development and succession of the 

 teeth in that rare Ruminant, which is the largest existing species of its 

 Order. The four middle deciduous incisors began to cut the gum one 

 week after birth, and their crowns were entirely extricated at the end 

 of four weeks, at which time the summits of the crowns of both the 

 first and second deciduous molars were visible. At two months the 

 third incisor had cut the gum ; at three months the third deciduous 

 molar, and at four months a fourth molar, were in place ; the latter 

 being the first of the permanent series of true molars. 



The progress of shedding the deciduous teeth was traced by 



(l) Anatomic Comparee du Systeme Dentaire, 8vo, 1S39, p. 229. 



