VEETEBRATA 



101 



Class v.— MAMMALIA. 



The primary characters of the Mammalia are seen in 

 their limbs and in their teeth. The general characters of 

 the skeleton may be learned from Fig. 37 (J^Xurodon sasvus 

 Leidy). The mutilate type of limbs is seen in Cdotherium 

 cepAa/us Cope (Fig. 45, facing page 108). The phalanges are 

 connected by integument and form an inflexible paddle, and 

 in the typical forms the elbow is also inflexible. The dif- 

 ference between unguiculate and ungulate phalanges may 

 be seen by comparing Fig. 37 and Fig. 55 (page 119) with 

 Figs. 38 and 39. The compressed curved form of the former, 

 adapted for prehension, is easily distinguished from the flat 

 generally wide type seen in the latter, which is adapted for 

 support. The different carpal and tarsal types of the Ungu- 

 lata are seen in Figs. 38 and 39. A, is the taxeopodous; B, 

 the proboscidian; C, the amblypodous; and D and E, the 

 diplarthrous, represented by the Perissodactyla (D) and Ar- 

 tiodactyla (E) respectively. 



The molar types of dentition in historical and develop- 

 mental order to the quadritubercular are represented in Fig. 

 40. Forms up to No. 5, inclusive, predominate in the Un- 

 guiculata ; and 6 and 7 with their derivatives predominate 

 in the Ungulata. The derivatives of Nos. 6 and 7 are 

 formed by the development of ridges or crests which cou- 



/v-^ 



GO) 



Fig, 40. — Diagrams of tjfpes of mammalian dentition, from Osborn ; 1, haplodont ; 2, pro- 

 todont ; S, triconodont ; 4, tritubercular superior and inferior ; 5, tritubercular superior, 

 tuberculo sectorial lower; 6, quadritubercular superior, quinquetuberoulur inferior; 7, quad- 

 ritubercular, both jaws, pr, protooone ; pa, paracone ; me, metacone. 



