PHYLUM Vni 



VKRTEBHATA 



259 



Fig. 365. 



Apteryx australis, Owen. Recent; New Zealand. Lefl lateral aspect of 

 pelvis, 3/ 4 . a, Acetabulum ; il, Ilium : is, Ischium : p, [lio-pectineal pr< 

 p', Pubis (after Marsh). 



111 flightless birds (Ratites) it may be quite smooth. The anterior end ma\ 

 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 j:>rocesses, one 



on either side, known 



as the costal processes, 



to which some of the 



abdominal or sternal 



ribs are articulated. 

 Thes/.-,///(Fig.364) 



is characterised by the 



earlv fusion of its 



constituent bones, 



especially those forming the brain case where the sutures are completely 



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



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 .n righl 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 

 quadrato-jugal, connects the equally slender maxilla with 

 the quadrate. 



The squamosal and periotic elements (prootic, epiotic, 

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

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



IV 



IV 



Fig. 366. 



Meleagris gallipavo, 

 Linn. Anterior (A), and 

 proximal (/;), aspect of 

 tarsonietatarsus of young 



individual. 



