canals for the vertebral arteries laterally ; and a hirmal canal for the carotid* 

 being formed below by u |x-rforation of the hy]Mi|>opliYsis, which is hen- niiu- 

 logoua to, but not homologous with, the lucnial arch in the tail of the cro- 

 codili- : tin- body of the vertebra forms the common centre of these four 

 canals. Huntrriatt. 



28. A typical vertebra of a Bird from the thorax of a Wild Swan (Cyynut fertu). 



The DempOfAjMI and spine have coalesced with each other and with th- 

 centrum : a short parapophysis is developed from the base of the neuraj>o- 

 physis, and a broad diapophysis from near the summit. The plcurapophysis 

 remains distinct, and articulates by its head to the parapophysis, and by it* 

 tubercle to the diapophysis. The hxmapophyscs (k) arc articulated to the 

 extremities of the pleurapophyscs, and the ca|iacious haemal canal or arch IK 

 completed by the expanded haemal spine (h) or ' sternum,' from which a me- 

 dian crest is developed. Thus the body of the vertebra is still the common 

 centre of an upper and lower and two lateral canals . but the lower or hu-mul 

 one has undergone an extraordinary expansion in relation to the lodgement 

 and protection of the great centres of the vascular system. 



Presented by Prof. Chcen. 



29. A typical vertebra from the thorax of an Ostrich, wanting the sternum or hirmal 



spine. The parapophyses (p), to which the heads of the pleurapophyses (pi) 

 are articulated, are developed from the sides of the centrum ; the diapophyse* 

 (</) from those of the neural arch ; the ha-mnpophyses (k) are expanded at 

 their lower extremities, where the arch is completed in the natural state, by 

 their junction with the sternum. llunteria*. 



30. A typical vertebra of a Mammal the second dorsal or thoracic of a Phalanger. 



The articular ends of the centrum are flat, which is a common, but not a con- 

 stant character of the vertebra? of Mammals. The neurapophyses (tut) have 

 coalesced together and with the centrum. The pleurapophyses (vertebral rib, 

 or pars ossea coat<r) remain distinct, and articulate by their head to the side 

 of the centrum, and by their tubercle to the diapophysis (</) : the ha-mapo- 

 physcs (sternal rib, or cartilago cotta) arc joined to the plcurapophyscs by one 



