116 INTRODUCTION. 



has two incisors, of which the right is usually found undeveloped within the 

 intermaxillary bone, while the left projects in the same line with the body to 

 the extent of several feet, being a straight, conical, spirally-twisted weapon, 

 analogous to the tusk of the Elephant. The Lamantins and Duyongs are 

 not properly ranked as Cetacea ; they are aquatic Pachydermata. Notice 

 has been purposely omitted of the Seal tribe (Phocidse), among which the 

 form and number, not only of the incisors, but of the other teeth, are too 

 variable to be the subject of a discursive review. The singular form 

 of the incisors in the Elephant and the Dinotherium has been noticed ; 

 but curiously abnormal forms of those teeth are met with where such 

 might be least expected. The Aye-aye, of Madagascar (Cheiromys), a 

 lemuridous animal, differs from all the Lemurs, in the form of these teeth, 

 and in the absence of canines. The incisors of this animal closely resem- 

 ble those of a rodent, having the same curve ; and those of the lower 

 jaw (as in the Beaver), sweep to the back of the ramus of the jaw, 

 beneath the roots of the molars : the points of the incisors resemble a 

 116 ploughshare. The ordinary Lemurs have (as seen in the 



accompanying figure, 116) four incisors above, small, and 

 placed in pairs, with a central space between them, into 

 which are fitted the points of the lower incisors and lower 

 canines. The lower incisors are four in number, long, 

 compressed, and fitted close together, so as to appear like 

 Teeth of Lemur. one tooth, serrated, or consisting of comb-like parts; 

 their direction is oblique. The lower canines, which resemble the in- 

 cisors in every respect, excepting that they are stouter, have been 

 long regarded as incisors ; but erroneously, as will be pointed out 

 117 hereafter. In the Galeopithe- 



are curiously formed : those of 

 the upper jaw are placed in 

 pairs ; those of the lower jaw are 

 also four : all are pectinated, 

 Teeth of Gaieopithecus. or, with a comb-like surface ; 



those of the lower jaw deeply and delicately, even to the commence- 

 ment of the root. The canines (if so they may be called) participate, 

 also, in this pectinated structure. 



The canine teeth are next to be considered. The upper canine tooth 

 (where present) succeeds the incisors at a greater or less interval ; it is the 

 first tooth on each side, in the true maxillary bones, the incisors being 

 always in the intermaxillary. The lower canine, on each side, always 

 advances before the upper canine, and is either in contact with its ante- 

 rior surface (as in the Tiger, fig. 118), fitting into a space between 

 that and the upper incisors ; or, as in the Horse (the male), it is not 



