400 



ANATOMY OF VEETEBEATES. 



205 



is a pair of liypapophyses on the fifth, sixth, and seventh caudal 



vertebrae. The pelvis con- 

 sists of five or six sacral 

 vertebra3 coalesced with each 

 other, also (1-4) with the 

 ilia, and (5-6) with the is- 

 chia, leaving wide ischiadic 

 foramina, fig. 266, d. The 

 sacral spines are obsolete, 

 and the centrums much de- 

 pressed. The ilia are short 

 and broad, forming an an- 

 terior concavity. The is- 

 chial tuberosities are small, 

 and the part joining the 

 pubis to circumscribe the 

 large obturator foramina is 

 slender. The pubis is also 

 slender, and forms a very 

 short symphysis, c. The 

 pelvic outlet is wide. 



In the Two-toed Sloths 

 (Cholcepus) the vertebral formula is C 7, B 23, L 3, s 8, cd 4, 

 or D 24, L 2 ; or D 23, L 4, s 7, the number being essentially the 



same. The second and 

 thn'd cervicals sometimes 

 coalesce. Cholcepus Hoff- 

 manni has only six cervi- 

 cals.^ Twelve pairs of ribs 

 join the sternum, which 

 consists of eleven bones. 

 Not any of the great extinct 

 Ground Sloths have more 

 than seven cervical verte- 

 brae ; but in the number of 

 dorsal vertebrae, as in every 

 other bradypodal character, 

 they manifest their true af- 

 finities. The Mylodon, fig. 

 267, offers a singular con- 

 trast with the Mole, fig. 248, in the proportions of the sacrum : 

 this, by anchylosis with the three lumbar and last dorsal, dls. 



Cervical and dorsal vertebriB, Ai. 



Pelvis of the Ai, anterior view. 



