11 



they are represented in the plates of the ' Ossemens Fossiles' di- 

 stinctly from the anterior zygapophyses, and exist in many vertebrae 

 after these processes with their articular surfaces have wholly dis- 

 appeared: the modifications of the metapophyses, and their mode 

 and place of superseding the prezygapophyses, are described in the 

 Delphinus Tursio and Z>. Delphis : their modifications are also 

 pointed out in the Dugong. But the most remarkable development 

 and complexity of the accessory exogenous processes is presented 

 by certain members of the Order Bruta or Edentata of Cuvier. 

 The author commences with a description of them in the Sloths, 

 and gives his reasons for considering the length of the neck in the 

 three-toed species to be due to the superaddition of two cervicals 

 between the dentata and eighth vertebra, which, from certain cha- 

 racters of its complex transverse process, he regards as homologous 

 with the sixth cervical vertebra of the two-toed species. 



In the Cape Ant-eater ( Orycteropus capensis)^ both metapophyses 

 and anapophyses are present on the eighth dorsal vertebra; the 

 former are continued to near the end of the tail, the latter subside 

 in the last lumbar. In the armadillos the metapophyses commence 

 abruptly about the middle of the back, and progressively increase 

 until they equal the long neural spines in height ; they develope two 

 articular surfaces, one on the inner side of their base, another on 

 the outer side : the latter articulates with the anapophysis, which is 

 remarkable for its thickness, and developes a second inferior articular 

 surface for the parapophysis, which, together with the diapophysis, 

 is developed from all the lumbar vertebrae. These complex jomts 

 are illustrated by drawings taken from two species of Armadillo. 



The exogenous processes present still greater complexity in the 

 true Ant-eaters. The metapophyses commence in the cervical 

 region, change their place from the zygapophyses to the diapophyses 

 in the anterior dorsals, and back again to the zygapophyses in the 

 posterior dorsal and lumbar vertebrae, where they supersede those 

 processes ; and develope accessory articular surfaces for the anapo- 

 physes. These not only present an upper articular surface for the 

 metapophysis, and a lower one for the parapophysis, but de- 

 velope a third outer one for a new articular surface upon the 

 diapophysis ; so that, were not the ordinary articular processes, 

 or zygapophyses, obliterated in the posterior dorsal and lumbar 

 vertebrae, there would be not fewer than eighteen synovial joints, 

 in addition to the intervertebral joints, in the posterior lumbar 

 vertebrae of the Great Ant-eater. These processes and articula- 

 tions are illustrated by figures taken from the Great Ant-eater; 

 and the necessity of the substantive names for the processes, and of 

 adjectives to signify their added articular surfaces, was exemplified 

 in the explanation of those figures. The peculiar complexity of the 

 vertebrae of the Edentata having been, previously to the investiga- 

 tions of the author, illustrated by a comparison with those of the 

 Serpent tribe, he next enters upon the question of the precise nature 

 and extent of this analogy, and shows that, although the complex 

 joints in both are comparable to the tenou-and-mortice joints in 



