328 THE ANATOMY OF VERTEBRATED ANIMALS. 



horns attain their full size very rapidly, and tben a circular 

 ridge, which makes its appearance at a short distance from tiie 

 root of the horn and is called the " hnrr" divides the horn into 

 the "pedicel" on the skull-side of the burr, and the '■'■beam" 

 on the opposite side. The circulation in the vessels of the heani 

 now gradually languishes, its integument dies and peels off, and 

 the dead bony substance beneath is exposed. Absorption and 

 sloughing next occur at the extremity of the pedicel, just as 

 might happen in any other case of necrosis. The beam and 

 burr are shed, and the end of the pedicel scabbing over, fresh 

 integument gradually grows up under the scab, and eventually 

 restores to the extremity of the pedicel its pristine smooth and 

 hairy covering. 



The rapidity with vchich the development of bony matter 

 into Deer-horn takes place is wonderful, horns weighing sev- 

 enty-two lbs. having been produced in ten weeks. 



The Cotylophora are represented in all parts of the world 

 except the Australian and Novo-Zelanian provinces. They 

 have not yet been traced back farther than the miocene epoch. 



c. The Camelidos or ( Tylopoda) are devoid of horns ; and, 

 unlike the other Ruminants, they walk upon the palmar and 

 plantar surfaces of the phalanges of the third and fourth toes, 

 which are alone developed. Broad integumentary cushions 

 form a sole to the foot; while the nails are flattened and can 

 hardly be called hoofs. 



The arches of the cervical vertebrae, and not their trans- 

 verse processes, are perforated by the canal of the vertebral 

 artery ; a character which the camels share with the Macrau- 

 chenidcB. 



The metacarpals are separated by a deep cleft, and the 

 distal phalanges of the digits are nearly symmetrical in them- 

 selves. The distal facets of the astragalus are more unequal 

 than in the other JRwninantia, and the navicular and cuboid 

 bones are not anchylosed together. 



The premaxillse have a single strong outer incisor on each 

 side. Large curved and pointed canines are developed in each 

 jaw, and are quite distinct from the series of the incisors in 

 the mandible. There are not more than five grinding teeth in 

 a continuous series above and below. 



The stomach is unlike that of the typical Ruminants. The 

 CEsophagus opens directly into the paunch, which is lined by a 

 smooth, not papillose, epithelial coat. From its walls, at 

 least two sets of diverticula, with comparatively narrow 

 mouths, are developed. These, the so-called "water-cells^^ 



