370 



SAUROPSIDA (birds). 



bone, whicli is made up of about half-a-dozen caudal vertebrae 

 fused into one piece, and constituting the support for the 

 tail-quills and oil-glands. These latter contain the fluid that 

 the birds proen their feathers with. 



The skull (fig. 209) articulates with the vertebral column by a 

 single condyle only. The beak (fig. 208, 10 and 11), so charac- 

 teristic of the Birds, consists of an inferior and superior mandible, 

 and never in existing species carries teeth. The upper bill (10) 



Fia. 210. — Pectoral Arch of Fowl. 



g.c. Glenoid cavity ; Sc, scapula : Co, roracoid ; Hp.C, h.vpocleidiuiii : /, fiircula 

 (clavicles). 



consists of greatly elongated intermaxillary bones and small 

 superior maxillary bones on each side. The lower jaw (11) 

 articulates with the skull by the quadrate bone (12), and not 

 direct as in mammals. The thorax is surrounded laterally by 

 the ribs (/ and /), ^vhich vary from .six to ten pairs : each rib 

 carries a peculiar process called (20) the "uncinate" process, 



