312 



ANATOMY OF VERTEBRATES. 



in the incompleteness of the rim of the orbit (vol. ii. p. 388, 

 fig. 253, A). The dental formula of the genus is 



247 



The two anterior incisors of the upper jaw are separated by a 



wide interspace. In the Phi- 

 lippine Colugo they are very 

 small, with simple sub-bilobed 

 crowns ; but in the common Co- 

 lugo (Lemur volans, Linn.; Ga- 

 leopithecus Temminckii, Wat.) 

 their crown is an expanded 

 plate with three or four tuber- 

 cles ; the second upper incisor 

 presents the peculiarity of an 

 insertion by two fangs in both 

 species of Galeopithecus. 



In the lower jaw the crowns 

 of the first two incisors, z, pre- 

 sent the form of a comb, and 

 are in this respect unique in the 

 class Mammalia. Fig. 249 

 shows a section of one of these 

 teeth magnified. This singular 

 form of tooth is produced by 

 the deeper extension of the 

 marginal notches on the crown, analogous to those on the edge of 



~ o 



the new-formed human incisor, and of those of certain Shrews, 



the notches being more nu- 

 merous as well as deeper. 



Each of these broad pec- 

 tinated teeth is implanted 

 by a single conical fang, and 

 is excavated by a pulp- 

 cavity, which divides into as 

 many canals as there are 

 divisions of the crown, one being continued up the centre of each 

 to within a short distance of its apical extremity. The medullary 

 canal or branch of the pulp-cavity is shown in some of the divi- 

 sions of the crown, at p. Each division has its proper investment 

 of enamel, e, which substance is continued for a short distance 

 upon the common base. 



The deciduous teeth appear not to cut the gum before birth, as 



Upper jaw and teeth, Galcopilhecus. 



218 



Lower jaw and teetli, Galeojnthccun. 



