TEETH OF DIPHYODONTS. 



313 



they do in the true Bats. In a foetus of Galeopithecus Tern- 

 minckii, with a head one inch and a half in length, I found the 

 calcification of the first incisor just commenced in the closed 

 alveolus, the second incisor 2-19 



and the rest of the decidu- 

 ous series being represented 

 by the vascular uncalcified 

 matrices. The upper milk 

 teeth consist of two incisors, p 

 a canine, and two molars, 

 which latter are displaced 

 and succeeded by the two 

 premolars. The deciduous 

 teeth are six in number in 

 the lower jaw, the incisors 

 being pectinated, but much 

 smaller than their succes- 

 sors. The true molars are 

 developed and in place be- 

 fore the deciduous teeth 

 are shed. 



E. Quadrumana. — In 

 entering upon the dentition 

 of the Quadrumanous order, 

 we pass from that of the 

 Insectwora by the Colugo, and seem to quit the Rodentia by 

 the Aye-aye ( Chiromys). In this genus of the Lemurine animals, 

 as in Phascolomys amongst the Marsupials, Desmodus amongst the 

 Bats, and Sorex amongst the Insectivores, the dentition is modi- 

 fied in analogical conformity with the Rodent type, to which, in 

 the present instant, it makes a very close approximation, the 

 canines being absent, and a wide vacancy separating the single 

 pair of large curved scalpriform incisors in each jaw from the 

 short series of molars. 



The upper incisors (vol. ii. p. 513, fig. 343, 22) are curved 

 in the segment of a circle, and deeply implanted. The short 

 exserted crowns touch one another, their simple widely exca- 

 vated fangs diverging as they penetrate the substance of the jaw. 

 These crowns also project obliquely forward, and do not extend 

 vertically downward, as in the true Rodentia. The lower inci- 

 sors are more depressed, and of greater breadth from before back- 

 ward, than the upper ones. They are more curved than in the 

 Rodentia, describing a semicircle, three-fourths of which are 



Section of lower incisor, Galeopithecus, magnified. 



