PHYLÜM \ni 



VERTEBRATA 



259 



in 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 JHH^^^^^^^^M^^Mt^ -.L^S^tKlM^^. it 



the front portion of 



the sternum, and im- 



mediatelybehind these 



are two processes, one 



on either side, known ^ 



as the costal processes, 



to which some of the 



abdominal or sternal y 



ribs are articulated. 



The5Ä;i*//(Fig.364) 

 is characterised by the ,, , ,. , „ Fio.sm. 



, , . / , Apteryx austrahs, Owen. Receiit ; New Zealantl. Left lateral aspect of 



early lUSlOn Ot itS pelvls, 8/4. a, Acetabulum ; il, Ilium ; is, Ischiuiii ; p, Ilio-pectiiieal process; 

 ^ ^ ^ „ - • 4. i i, P', Pubis (after Marsh). 



constituent bones, 



especially those forming the brain case where the sutures are completely 



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

 ij, the parietals and frontals seems to remain permanently 



open. The brain cavity is relatively less diminutive than 

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

 siderable margin. The cranial osteology is very similar to 

 that of the Archosauria, the chief difference 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, 

 and there is, of course, no supratemporal vacuity. The 

 inferior temporal arcade, formed by the slender jugal and 



i.in... Anterior (^X and quadrato-iugal, couuccts the equallv slender maxilla with 



proximal (/>'), aspect of ^ J ö J i ./ 



tarsometatarsusofyoung the Quadrate. 



ludividuai. rj^j^g squamosal and periotic Clements (proötic, epiotic, 



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

 [)arietals, and to which the large quadrate is movably attached. An independent 



Fig. 



Meleagris 



galliparo. 



