v.J ' PRIMATES. 47 



terior zygapophysis ; this is the metapophysis, or mammillary j 

 process. The other projects backwards, and represents in ; 

 a rudimentary condition the process so largely developed in | 

 many animals called anapophysis. It gradually becomes 

 smaller in the second and third lumbar vertebrae, and gene- ] 

 rally disappears in the fourth. 



The lumbar transverse processes are thus not serially 

 homologous with the thoracic ribs, but with the part of the 

 transverse process of the thoracic vertebrae to which the 

 tubercle of the rib is attached, and are complementary to 

 the ribs, becoming greatly augmented in size directly these 

 cease. Neither are they normally developed autogenously. 1 



The sides of the bodies of the thoracic vertebrae bear 

 facets for the articulations of the heads of the ribs. Except 

 the last three or four, each vertebra supports a portion of the 

 heads of two ribs, having a large facet near its anterior edge 

 (placed partly on the body and partly on the side of the 

 pedicle) for the head of its own rib (i.e. the rib which arti- 

 culates also with the transverse process), and on the hinder 

 border of the upper angle of the body a small facet to re- 

 ceive the anterior edge of the succeeding rib. In the hinder 

 part of the thoracic region the rib is connected only with 

 its corresponding vertebra, and not with the one in 

 front. 



Among the remaining Primates, 19 is the prevailing 

 number of trunk vertebrae, of which usually 12 to 14 bear 

 ribs. The Gorilla and Chimpanzee (genus Troglodytes), 

 agree with Man in having 17. The Orang (Simia) has 

 usually but 16. The Gibbons (Hylobates) and Spider 



1 There are several specimens in the College Museum which show 

 the co-existence, on the first lumbar vertebra, of a rudimentary (supple- 

 mental) rib, with a transverse process serially homologous with the 

 transverse processes of the other lumbar vertebrae. 





