PHYLUM VIII 



VEETEBEATA 



259 



Fig. 365. 



Apteryx austrcdis, Owen.VJRecent ; New Zealand. Left lateral aspect of 

 pelvis, 3/^. a, Acetabulum ;lil'''f\iura ; is, Ischium ; p, Ilio-pectiueal process; 

 p', Pubis (after Marsh). 



ill flightless birds (Ratites) it may be quite smooth. The anterior end may 

 or may not bear a manubrial process, the posterior portion may be pointed, 

 rounded, emarginate, ■ 



or have two or four - ' ^~^^ 



notches, sometimes 

 very deep. The cora- 

 coids are attached to 

 the front portion of 

 the sternum, and im- 

 mediately behind these 

 are two processes, one 

 on either side, known 

 as the costal processes, 

 to which some of the 

 abdominal or sternal 

 ribs are articulated. 



ThesA-».//(Fig.364) 

 is characterised by the 

 early fusion of its 

 constituent bones, 

 especialljT^ those forming the brain case where the sutures are completely 

 obliterated in the adult. In the tinamous, however, the suture betAveen 

 1^ the parietals and frontals seems to remain permanently 



0'*TN^ open. The brain cavity is relatively less diminutive than 



/I in reptiles, exceeding even that of Pterosaurs by a con- 



II IV siderable margin. The cranial osteology is very similar to 



that of the Archosauria, the chief diff'erence consisting in 

 the constant absence of an upper, and constant presence of 

 a lower temporal arcade. The large orbits look forward 

 in the owls, but are laterally directed in the majority of 

 birds, and except in parrots are incompletely enclosed on 

 the inferior margin. A sclerotic ring of numerous bony 

 pieces is very generally developed around the eye. An 

 antorbital vacuity is present, as in Dinosaurs, Pterosaurs, 

 and Crocodilians, close in front of which, near the base of 

 the beak, are placed the paired external narial openings. 



The single occipital condyle, formed mainly by the 

 basioccipital, is shifted downwards and forwards so that 

 the long axis of the head is approximately at right angles 

 to that of the neck. The paired parietals are exceeded in 

 size by the large frontals, which form the greater part of 

 the cranial roof and superior border of the orbits. Inde- 

 pendent postorbitals and postfrontals are not developed, 

 pj^ ggg and there is, of course, no supratemporal vacuity. The 



Meieagris gaUipavo, inferior temporal arcade, formed by the slender jugal and 

 proxi'mai"(5f°aspect^'of O[^a,drato-jugal, connects the equally slender maxilla with 



tarsometatarsus of young the QUadrate. 



individual. Jii i i • • i /..... 



ihe squamosal and periotic elements (prootic, epiotic, 

 and opisthotic) fuse to form a single bone which is united Avith the occipital and 

 parietals, and to which the large quadrate is movably attached. An independent 



