PACHYDERMATA. 



865 



In tlie Hippopotamus, the Rhinoceros, and 

 the Tapir, the separation of the toes is more 

 apparent externally, but still the phalanges, 

 which are three in number to each of the four 

 toes, are excessively strong and bulky when 

 compared with their length. A kind of grada- 

 tion is likewise to be traced through these 

 genera, whereby the foot of the Elephant be- 

 comes gradually transformed into the cloven 

 hoof of the hog tribe, owing to the progressive 

 diminution in size of the inner and outer toes, 

 and the gradual conversion of the terminal 

 phalanges of the central toes into that prismatic 

 form which adapts them to fit the horny enve- 

 lopes that encase them like shoes. 



Throughout all the hog genera the weight of 

 the body is entirely supported on the two cen- 

 tral digits, the bones whereof are propor- 

 tionally strong and well developed, while the 

 phalanges of the inner and of the outer toe, 

 which do not louch the ground, remain per- 

 manently of very rudimentary size. 



Teeth. In no order of Mammiferous ani- 

 mals do the teeth present so much diversity of 

 structure and irregularity of disposition as 

 among the Pachydermatous races ; it will be 

 therefore necessary, in adverting to this part of 

 their economy, to describe the principal modifi- 

 cations which the dental organs assume in 

 different genera, before we proceed to investi- 

 gate the manner of their formation; and this we 

 do more willingly, because from the character 

 and arrangement of the teeth we can alone sa- 

 tisfactorily determine what have been the habits 

 of extinct genera, the list of which is already 

 considerably more extensive than that of living 

 forms. Professor Owen, to whose labours in 

 this department science is already so deeply in- 

 debted, has in his recent work on the Com- 

 parative Anatomy of the Teeth* examined this 

 part of our subject with all the minuteness re- 

 quired for geological researches, and from his 

 kindness we are enabled to lay the following 

 abstract before our readers. 



In the genus Sus, the wild progenitor of our 

 domestic breeds of Hogs, Sus scrofa, the com- 

 plete set consists of forty-four teeth, viz. 



Incisor. Canine. Premolar. Molar. 



5.3 1.1 4.4 3.3 



3.3 1.1 4.4 3.3 



In the wild Boar both the upper and lower 

 canines curve forwards, outwards, and up- 

 wards ; their sockets inclining in the same di- 

 rection, and being strengthened above by a 

 ridge of bone which is sometimes extraordina- 

 rily developed, these teeth become converted 

 into most formidable weapons. These teeth, 

 which have the character of true tusks, are 

 three-sided ; the broadest convex side being 

 directed obliquely inwards and forwards, while 

 the outer and posterior sides are nearly flat; and 

 the hinder surface being destitute of any cover- 

 ing of enamel ; whilst the two other sides are 

 encased with that material, the tusk wears ob- 

 liquely from behind upwards and forwards to 

 a point, while its posterior margins present 



* Oclontography, Bailliere, 8vo. 1845. 

 VOL. III. 



enamel edges that are always sharp and tren- 

 chant. Each of these tusks in the lower jaw 



Fig. 477. 



of the German wild Boar will measure eight 

 inches in length along its curve, and in the 

 wild Boars of Assam they have been noticed 

 measuring one foot, so that when wielded by 

 such strong and brawny muscles as those of a 

 Hog's neck, it is easy to conceive that terrific 

 wounds may be inflicted by such instruments. 



In the Baberoussa or " Horned Hog " the 

 developement of the canines is still more ex- 

 traordinary. Those of the upper jaw seem as 

 if their sockets had been pulled out or pro- 

 duced from the alveolar border of the upper 

 maxillary bone, and then abruptly bent up- 

 wards, giving the tooth a direction upwards 

 and backwards. The tooth pierces the integu- 

 ments of the upper lip like a horn, and its 

 growth being unchecked by any opposing tooth, 

 sometimes forces the lip again through the in- 

 tegument and into the substance of the skull. 

 The lower tusks have the ordinary direction, 

 but rise rather more vertically and much higher 

 than in the wild Boar. These strangely situated 

 teeth are well adapted by their position to de- 

 fend the eyes and assist in the act of forcing 

 the head through the dense entangled under- 

 wood of a tropical forest, as suggested in 

 Home's Comparative Anatomy, vol i, p. 221, 

 but their use has not been determined by actual 

 observation. 



In the next group of Pachydennata (C/xero- 

 potamidtf) the dental formula of the existing 

 type of the family Dicotyles, the Pcccari, is 

 as follows. 



Incis. Canine. Premolar. Molar. 



2.2 1.1 3.3 3.3 



3.3 1.1 3.3 3.3 



The upper canines are moderately long, narrow, 

 and compressed, with an entire covering of 

 enamel ; while the lower are long, slightly 

 curved, and have no enamel posteriorly. To 

 this type of dentition belonged the Hyracothe- 

 rium and the Cfiaropotumus, both extinct genera, 

 the former having been about half the size of 

 the existing Peccari, while the latter was about 

 one-third larger. The Hippophyus, likewise 

 an extinct genus, found in the Himmalayan 



3 K 



