SUBORDER B 



FISSIPEDIA 



61 



to one or two. In purely carnivorous forms, the crowns are broader than 

 long, and trituberculate ; while in omnivorous carnivores they are quadri- or 

 multituberculate. The posterior molars degenerate or disappear as the diet 

 becomes more exclusively carnivorous ; on the other hand, in the frugivorous 

 bears and Mustelidae the premolars exceed the carnassials in size. There may 

 be one or two lower molars in addition to the carnassial, their crowns 

 consisting of a bilobed anterior portion and a talonid. M^ is often very 

 small or may disappear. 



In the milk dentition (Fig. 87), D^ is essentially like 31-^, and the lower 

 carnassial Dg like P^. In the upper jaw, also, D^ is, on the whole, similar 

 structurally to ilf\ and D^ to P"^, and D'^ is very like F^. All of the milk 



teeth are, however, slenderer than those of 

 the mature dentition. D^ has, as a rule, no 

 inner basal cingulum, the lower D^has rather 

 a large talonid, and the inner cusp of D^ 

 is placed more posteriorly than on P^. The 



di dc dm^ dm^ : J 



dm,, 



Fig. SS. 



Milk dentition of Viverra civetta Linn. (After Maniis, A, of dog and B, of bear. R, Radius ; U, ulna ; 



Mivart.) A, B, Inferior and lateral aspect of l+sc, scapho - lunar ; c, cuneiform (triquetrum) ; p, pisi- 



upper jaw. C, D, Lateral and superior aspect of form ; u, unciform ; in, magnum ; td, trapezoid ; tz, tra- 



lower jaw. pezium ; 7?ic, metacarpals ; I.-V., first to fifth digits. 



roots of all the deciduous molars are more widely divergent than those of the 

 premolars. 



The pectoral girdle sometimes includes a rudimentary clavicle, and 

 the humerus may possess an entepicondylar foramen. Radius and ulna 

 remain distinct. Usually five digits are present, of which the first is 

 generally much shorter than the others (Fig. 88). In the cats and civets, 

 the pointed ungual phalanges are capable of retraction over the second 

 phalanges. The femur always lacks a third trochanter. The tarsals 

 are closely crowded, the fibula has an articular surface for the calcaneum. 



