HOG-TRIBE. 559 



slightly curved lines, with the feeble convexity turned towards the 

 periphery. 



In the middle of the transverse section of the dentinal prism, 

 a narrow tract of osteo-dentine is seen surrounding the area of 

 the central vascular canal : it is characterized by its more trans- 

 parent texture ; its fewer and more contorted tubuli, and the minute 

 opake cellules dispersed through it. The clear substance is arranged 

 in concentric layers around the canal, and the outer boundary 

 of this small sub-circular patch of osteo-dentine is very well defined 

 from the true dentine : the central ends of the tubes of this 

 tissue are closely crowded round the clear boundary of the osteo- 

 dentine, but a very few are traceable into that substance. 



The enamel-fibres, as exposed by a vertical section of the 

 complex tooth, extend obliquely upwards and outwards in a straight 

 line, for the first half of their course, then bend outwards to the 

 periphery of the enamel, which is very irregular. The transverse 

 section of the cylinder of enamel displays a strong wavy, or crenate 

 outline : the rounded lobes which project into the cement being 

 of nearly equal breadth with the intervening notches. The contour- 

 lines of the enamel are well shown in this section, and alter their 

 course from the parallel of the even margin of the dentine to 

 that of the crenate outer margin of the enamel. 



A very small outer part of the exterior cement of the molar 

 is nearly clear, with the fine cemental tubes penetrating the substance 

 at right angles to the surface. A thick and densely aggregated 

 stratum of Purkingian cells, mostly of a full oval figure, are next 

 seen, these cells being rather less thickly arranged in the middle 

 of the cement. The vascuar canals of the cement are chiefly 

 present near the enamel ; some were seen forming loops turned 

 towards the outer surface of the cement. 



200. ChcBropotamidcB. — The dental formula of the Peccari 

 {Dicotyles,) is : — 



Incisors -^ ; canines — ; premolars — - ; molars — - : = 38. 



3—3 1 — 1 3 — 3 3—3 



The two middle upper incisors are the largest, and are thick, 

 short, curved and convergent, as in the Hog. The external surface 



