WART HOGS. 551 



in PI. 140, fig. 4, and in the figures given by Dr. Riippell. In 

 the young individual, the crown of the first true molar (PI. 141, fig. 1, 

 m 1) is divided into two principal lobes, each lobe resembling the 

 entire crown of the last premolar, and having a central enamel- 

 island surrounded by four or five similar peripheral ones : it is 

 implanted by four long and strong fangs ; the antero-posterior 

 diameter of the grinding surface measures nine lines. The second 

 true molar (PI. 140, fig. 4, & PI. 141, fig. 1 & 2, m 2), which does 

 not cut the gum until the first is more than half worn down, 

 presents a broader subquadrate crown, nine lines by seven lines 

 across the grinding surface, which presents a central enamel island, 

 surrounded by four principal and some smaller islands or lobes. 

 The third and last true molar (ib. m 3) is the most characteristic 

 tooth of the Phacocheres, and perhaps the most peculiar and 

 complex tooth in the whole class of Mammalia : the surface of 

 the crown in the specimen before me, measures two inches in 

 antero-posterior extent and eight lines in transverse breadth, and 

 presents three series of enamel-islands, in the direction of the 

 long axis of the grinding surface : the middle row of eight islands 

 are elliptic and simple ; those of the other rows are in equal 

 number, but are sometimes subdivided into smaller islands : 

 these islands or lobes are the abraded ends of long and 

 slender columns of dentine, encased by thick enamel, and 

 the whole blended into a coherent crown by abundant cement, 

 which fills up all the interspaces and forms a thick exterior 

 investment of the entire complex tooth. In the closed alveolus 

 of the third molar of a young Phacochere, I found a number of 

 the hollow prisms of enamelled dentine detached (PI. 141, fig. 1, 

 m 3) : the formative matrix continues for a long jDcriod to be 

 reproduced, maintaining by its successive calcification the crown of 

 the tooth entire to the bottom of the socket, where the orifices of 

 the constituent cylinders and the vacant interspaces, which lodged 

 the complex vascular matrix are seen in the dried tooth. 



In the lower jaw of the Nubian Phacochere the four middle 

 incisors are strong, subtetragonal, porrect, subequal, with the ridge 

 and grooves upon the upper side of the crown as in the ordinary 



