736 COMPARATIVE ANATOMY 



Cs, Left superior carnassial, seen from the crown. 



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

 3 1 4 3 (2) 



Dental formula : 



3133 



6. Ur sides (Bears). The least carnivorous of all the Carnivora. They originated, apparently, 

 in the upper Miocene, from the primitive Canides (Amphicyon). 



Type Figure : Ursus arctos L. 



17, , The two jaws seen from the right side. 



U n , Left half of the base of the skull seen from the lower aspect. 



This figure has been placed near the corresponding figure of the Lion in such a manner as to 

 render apparent the comparison between these two extreme types. The comparison must be 

 limited to the portion included in each figure between the incisive teeth and the occipital condyle 

 (co). Behind this there is a very large hollowed out area which projects from the posterior 

 aspect, to serve as the inservation of the posterior muscles of the skull and neck. 



Us, Left superior carnassial, seen from the crown. 



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

 3132 



Dental Formula : 



3123 



This is probably a regressive adaption to the omnivorous regime. The enormous development of the 

 molars have become quadrituberculated and complicated by. the appearance of little tubercles on or 

 between the greater tubercles. Regression of the cutting function of the teeth has followed, 

 the flesh-eating character becoming hardly apparent except in the remarkable power of the upper 

 canines, "with their very oblique insertion and long root. The skull also lengthens. 



Changes which take place in the Superior Carnassial Teeth: (Figs. Vs, Hs, Fs, Ms, Cs, Us. 

 In the figures the arrow indicates the upper teeth, l;he arrow's point being directed toward the 

 opening of the mouth). 



a, paracone or antero-external cusp; a', anterior accessory cusp; 5, protocone, or antero- 

 internal cusp ; c, metacone, or postero-external cusp. 



Primitive form ( Viverra, Vs) ; type trigodont (triconodont). The tooth contains two ex- 

 ternal cusps (a,c) compressed laterally and united in a single cutting edge, and a third tubercle 

 (6) placed anterior and forward. A fourth tubercle (a') is often found in front of the two 

 external cusps on the same line with them. The cutting edge formed by these last is lengthened in 

 such a manner as to place these tubercles together and thus present three points. The tooth has 

 three roots, two anterior and one posterior. 



Hyaenidae and F 'elides (Hs and Fs) : The external cutting edge is developed highly in these. 

 The internal anterior tubercle remains conical and blunt, but disappears completely in Machairodus 

 (Ms). 



Canides: (Cs) : Changes in the omnivorous group. The tubercle a' has disappeared, the 

 tubercle 6 remaining prominent. 



Ur sides: (Us) : There is the same type of accentuation as in the Canides. Three conical 

 tubercles. 



Changes in the Lower Carnassial: (Figs. Ui, Ci, Hi, Fi, Vi) . The arrows are placed above 

 the tooth to indicate the lower ones. The point indicates the anterior direction, a, paraconid or 

 anterio-internal cusp; B, protoconid or external-anterior cusp; B', metaconid or internal posterior 

 cusp ; Y, hypoconid, or posterior talon. 



The primitive type (Viverrides, Vi) is here the tuberculo-sectorial type of Cope. It contains 

 (1), An anterior part with three tuberculated points: two internal, A, B' , and one external, 

 B, (2) a posterior talon Y, low and flattened, carrying one or more blunt tubercles. The tooth 

 presents, in other words, a secodont anterior portion (carnivorous) and a tuberculated posterior 

 portion (omnivorous). It has two roots corresponding to the two parts. 



This tuberculo-sectorial type is common to all the lower molars of the creodonts and is limited 

 more or less to the true carnassial tooth in the true Carnivora. 



Canides. Ci : The tuberculo-sectorial type is preserved but with accentuation of the carnassial 

 character. Then there is a reduction of. the talon predominance of B, reduction of B' , and the 

 anterior root is somewhat stronger than the posterior. 



Hyaenidae, Hi. : Regression of the talon ; the tubercles A and B compressed and united in 

 a sharp cutting edge, and bicuspid; B' notably reduced. The anterior root is much stronger 

 than the posterior. 



F elides, Fi.: The talon of B' has nearly disappeared and there is predominance of the anterior 

 root. 



Ursides, Ui. : Omnivorous type ; the secodont part is smooth ; its tubercles are blunt and 

 conical ; the talon contains more than half of the crown ; it is covered by the secondary tubercles, 

 which are elevated almost to the level of the anterior cusps. The whole of the talon has this one 

 surface entirely similar to that of the tuberculated molars which are placed next in position. 



Title Figures: P, head of Panther (FELIS) ; Ci, head of Civet (VIVERRA) . (From the 

 charts of Remy, Perrier & Cepede). 



There are four kinds of teeth in mammals (Fig. 431). In the human 

 being they are alike in both upper and lower jaws, as well as alike in both 

 halves of upper and lower jaws. For classification of teeth, we use only 

 one-half of the teeth in either jaw. Thus in man we find the two teeth 

 nearest the midline the incisors are followed by a single canine. This 

 is distinctly cone shaped and has a single root. Back of this come the 

 two pre-molars commonly called bicuspids, having 1 two roots and com- 

 plicated crowns. They appear both in the milk and permanent den- 



