vi.) RODENT1A. 73 



Solenodon, Gymnura, Potamogalc^ Aficrogale (43 vertebrae), 

 Tupaia and Rhynchocyon ; in the last-named genus the 

 chevron bones are well developed and bifid. 



In the CHIROPTF.RA, the tail is sometimes exceedingly 

 rudimentary, as in Destnodus and Pteropns ; sometimes elon- 

 gated, but composed of long, simple, slender, cylindrical 

 vertebral bodies ; and generally enclosed in the interfemoral 

 cutaneous expansion. 



Among the different members of the order RODENTIA, 

 there are great differences in the condition of the caudal 

 vertebrae. 



In the Hares, Guinea Pigs, Capybara, &c, the tail is 

 almost rudimentary. In the Cape Jumping Hare (Ptdetes) 

 it is nearly as long and powerful as in the Kangaroo, and 

 has well-developed chevron bones. 



In the true Porcupines the tail is generally short ; but in 

 some allied genera (Tree Porcupines) it is much elongated 

 and prehensile. 



In the lleaver (Castor) there are 24 caudal vertebrae, all 

 short, broad, and depressed, and with wide transverse pro- 

 cesses, becoming double (anterior and posterior) about the 

 middle of the tail, not by development of a new process, 

 but by gradual division of the one existing in the anterior 

 region. 



In the UNGULATA, the tail is variable in length, but of 

 simple character and function ; it is never prehensile, 

 nor has it ever chevron bones, although occasionally, as 

 in the Ox, a pair of well-developed hypapophyses may be 

 produced so as to meet in the median line, enclosing a 

 small canal. 1 The vertebrae are most numerous (about 16 



1 The Eocene Anoplotherium appears to have had chevron bones 

 beneath the vertebrae of its long tail. 



