IV.] MARSUPIALIA. 41 



In the Armadillos {Dasypodidce) the bodies are extremely 

 short, broad, and depressed, and several are commonly anky- 

 losed together ; the corresponding neural arches being also 

 united, the neural and vertebrarterial canals form continuous 

 tubes. The orifices for the spinal nerves perforate the united 

 pedicles. The atlas is always free. The vertebrae that are 

 united are the second and third, or the second, third, and 

 fourth, and in some species the fifth also. The spinous 

 process of the axis is very large, but the neural arches of the 

 hinder free vertebrae are extremely narrow, and the spinous 

 processes rudimentary. The transverse process of the 

 seventh has an inferior lamella, nearly as large as that of 

 the sixth, but it is usually not perforated. 



In Orycterofius, the Pangolins (Mams), and the Anteaters 

 (Myrmecophaga), the neck vertebrae are more normal in form, 

 and are not ankylosed. In the last-named genus, the verte- 

 brarterial canal of several of the vertebrae perforates the 

 pedicle obliquely, and enters the neural canal posteriorly, 

 much as in the Camels. 



Among the leaf-eating Edentates, or Sloths, the neck 

 vertebrae present some remarkable peculiarities, especially 

 as to number. 



All the known species of three-toed Sloths (genus Brady- 1 

 pus) have nine cervical vertebrae, i.e. nine vertebrae in front of ( 

 the one which bears the first thoracic rib (or first rib con- 

 nected with the sternum, and corresponding in its general 

 relations with the first rib of other Mammals), but the ninth, 

 and sometimes the eighth, bears a pair of short moveable 

 ribs. The eighth is perforated by the vertebrarterial canal, 

 but not the ninth. 



The common species of two-toed Sloth ( Cholozpus didac- 

 tylus) has seven cervical vertebrae, but a closely allied 

 species (C. hoffmamiii) has but six. 





