DIGESTIVE SYSTEM 735 



.Premolars becoming complicated from before backward, to pointed tuberosities, and compressed 

 laterally (secodont type) ; the fourth premolar (p 4 ) and the three upper molars united to three 

 tuberosities by sharp ridges. On the lower jaw, these teeth present the entire anterior surface to 

 three pointed tubercles and a flattened posterior heel (Type: tuberculo-sectorial of Cope). 



II. CARNIVORA. They are distinguished from the Oeodonts, from the point of view of 

 dentition, by the differentiation in the two jaws, of a carnassial, or tooth of slicing action, made 

 apparent by its greater development than that of the other molars. It is the 4th premolar of the 

 upper jaw ; in the lower jaw it is the 1st molar. 



In a general manner, all the teeth placed before the carnassial, that is to say all the premolars, 

 are sharp-pointed ; all those which are behind it are tuberculated. 



1. Viverrides (Civets) : The most primitive of the Carnivora properly speaking (true Oligo- 

 cene), from which all the other forms are usually considered to have been derived. Type shown: 

 Viverra indica Desm. 



V, skull, seen from the right side. The maxillae have been dissected away sufficiently, as in 

 the other figures, so as to show the roots of the teeth. 



Vs, left superior carnassial tooth, seen from the crown. 

 Vi, left inferior carnassial, seen from the internal aspect. 

 3 1 4 (3) 2 



Dental formula 



3 1 4 (3) 2 



The number of molars is in general reduced to two, characteristic of a carnivorous specializa- 

 tion. 



2. The Mustelids (marten, sable, polecat, weasel, stoat) are very close to the primitive type. 

 The carnivorous tendency is strongly developed, as shown by the great reduction of the molars 

 and the higher development of the carnassial tooth. 



Starting from the Viverrides, the various forms of the carnivora show changes in two clearly 

 divergent directions : one, in which the meat-eating nature of the animal becomes more and more 

 evident, as in Hyaenidae, Felides, and Pinnipedes (seals, eared seals, walrusses) and the other which 

 returns somewhat to the omnivorous order, separated from the Hyaenidae and Felides, and giving 

 rise to the Canides and Ursides. 



3. Hyaenides: These form a branch supposedly derived in a direct line from the Viverrides 

 (Hyaenictia) as they appear in the upper Miocene. 



Type Figure: Hyaena Crocuta L. 



H, the two jaws, seen from the left side. 



Hs, left superior carnassial tooth, seen from the crown. 



Hi, left inferior carnassial tooth, internal view. 



3141 

 Dental Formula : 



3131 

 dentition quite like that of felides, and not well developed in a carnivorous sense. 



4. Felides (cats) : The most characteristic of the Carnivora. Their most typical representa- 

 tives appear in the Miocene type, but they are preceded by others, which connect them with the 

 viverrides. 



Type Figure: The lion (Felis Leo L.) ; Machairodus cultridens Cuvier, (a fossil Feline of 

 the European Pliocene age). 



F lt Skull of a lion, seen from the left side. 



F^, Left half of the same skull, seen from below. 



F 3 , Left superior carnassial, seen from the crown. 



Fi, Left inferior carnassial, seen from the internal aspect. 

 3131 



Dental Formula 



3121 



Of the tuberculated molars, a single one persists, very much reduced (m 1 ). The premolars, 

 although secondont, have undergone a certain reduction in their number as well as in their size, 

 leaving all the functional importance to the carnassials, which have become enormous. The 

 canines are likewise very strong, and are much longer than their neighbors. On the other hand, 

 the incisors, whose cutting function is done much more efficiently by the carnassials, have di- 

 minished. The jaw is, all in all, greatly shortened. Notice also the great development and widen- 

 ing of the zygomatic arch, giving a large surface for the levator muscles of the lower jaw (the 

 temporalis, which passes under the arch, and the masseter, which takes its origin from the entire 

 length of the arch). It has thus acquired considerable size and strength. The lower jaw is 

 greatly hollowed out on its external aspect, to permit insertion to the fibers of the large masseter 

 muscle. 



M, Skull of Machairodus cultridens (extinct saber-toothed tigers), seen from the left side. 



Ms, left superior carnassial, seen from the crown. 



An exaggeration of the Feline type. 

 3120 



Dental formula 



3111 



Huge development of the superior canine teeth, which surpass so far those of the lower jaw that 

 they limit closely, on each side, the buccal gap, no longer permitting free use of the canines and 

 carnassials in tearing off meat. 



5. Canides (dog-like carnivora). A mixed group, both meat-eating and omnivorous. The 

 canides appear early in the Oligocene, their first forms being closely related to the primitive 

 Viverra or to the Creodonts, some of whose characteristics are even more primitive than those of 

 the typical Viverrides. The dog family appears in the early Pliocene. 



Type Figure : Canis familiaris, L. 

 C. Left half of the skull, seen from below. 



C', Left inferior maxillnry condyle. seen as a horizontal cylinder (characteristic of all the 

 Carnivora) in relationship with the j?l~nr>M cavity which is hollowed out cylindrically. 

 C , The skull, seen from the right side. 



