490 MANUAL OF ZOOLOGY SECT, xn 



bear great expanded lateral plates sacral ribs with rough- 

 ened external surfaces for articulation with the ilia. 



Of the caudal vertebrae the more anterior resemble those 

 of the sacral region and have similar processes ; but as we 

 pass backwards in the caudal region all the processes gra- 

 dually diminish in size, the most posterior vertebrae being 

 represented merely by nearly cylindrical centra. 



There are twelve pairs of ribs, of which the first seven are 

 true ribs, i.e. are connected by their cartilaginous sternal ribs 

 with the sternum ; while the remaining five, the so-called 

 false or floating ribs, are not directly connected with the 

 sternum. All, except the last four, bear two articular facets, 

 one on the vertebral extremity or capitulum, and the other on 

 a little elevation or tubercle situated at a little distance from 

 this, the former for the bodies, the latter for the transverse 

 processes of the vertebrae. 



The sternum consists of six segments or sternebrce, the 

 first or manubrium sterni or presternum (Fig. 278, ps.) is 

 larger than the rest, and has a ventral keel. With the last is 

 connected a rounded cartilaginous plate, the xiphi sternum. 



The skull (Fig. 277), if we leave the jaws out of account, 

 is not unlike that of the Pigeon in general shape. The 

 length is great as compared with either the breadth or 

 the depth ; the maxillary region, or region of the snout 

 (corresponding to the beak of the Pigeon), is long in propor- 

 tion to the rest, the orbits closely approximated, being separ- 

 ated only by a thin interorbital partition, and the optic 

 foramina united into one. But certain important differences 

 are to be recognised at once. One of these is in the mode 

 of union of the constituent bones. In the Pigeon, as we 

 have seen, long before maturity is attained, the bony elements 

 of the skull, originally distinct, become completely fused 

 together so that their limits are no longer distinguishable. In 



