OSSEOUS SYSTEM OF AVES. 65 



stricted to the space above the orbits, in Oreophasis Derhyanus : 

 the bony extensions of the upper part of the premaxillary in 

 certain Hornbills, especially Buceros galeatus : the elevated base 

 of the short and thick upper mandible in Ourax Pauxi; the 

 multiplied superorbitals in Tinamus, Nor, perhaps, should the 

 spherical bony cyst above the fore part of the cranium in a 

 variety of common fowl be omitted, though this, like the stunted 

 mandibles of some varieties of pigeon, may rather rank among 

 the phenomena of pathology. 



§ 129. Scapular Arch and Appendage. — The simplest condition 

 of this arch is manifested in Apteryx and Dinornis, It consists 

 of scapula and coracoid, uncomplicated by connection with the 

 liiBmapophysis of any other segment : moreover, the pleur- and 

 haem-apophyses of the occipital rib have coalesced. A man must 

 shut his eyes, and with a tight squeeze, to escape recognising the 

 significance of the propinquity of the scapular arch to the 

 hyoidean one in the embryo bird. As developement proceeds, 

 segment after segment is added to the cervical series, and the 

 occipital ribs, with the myelonal centres supplying their appen- 

 dages recede far back from the typical jx)sition they maintain in 

 the Fish (vol. i. figs. 34, ^5, 5i, 52). In Dinornis, as in Murcena 

 and Any ids, the arch has no appendages. The scapula is rib- 

 like, compressed, slightly bent, measuring but 4J inches long in a 

 species (Z). robustiis) with a tibia a yard long ; it is barely an inch 

 across its broadest end where it coalesces with the coracoid, and 

 the breadth of the opposite free end is but 5 lines. The coracoid 

 is straight, 2 inches 10 lines long, ^ inch broad, becomes thicker 

 to its sternal end, which is convex and adapted to the small 

 ' coracoid ' fossa at the angle of the sternum. There is no trace 

 of glenoid cavity at the confluence of the two bones, but the 

 confluent part is here produced into a ridge, showing that there 

 was no humerus, and that the fore-limb, or appendage of the 

 scapular arch, was wholly absent in Dinornis, 



In Apteryx the scapula is relatively more expanded where it 

 coalesces with the coracoid, and the bone is broader in proportion 

 to its length, and shows a vascular perforation near the humeral 

 articulation, as in the Monitor (vol. i. p. 174). The glenoid 

 cavity is very small, but of the usual shape in Birds. In these 

 the scapular arch includes on each side a scapula, fig. 19, 51, a 

 coracoid bone, ib. f 2, and a clavicle, ib. 58 — the clavicles, coalescing 

 in most birds at their mesial extremities, constitute a sino^le 

 bone, which, from its peculiar form, is termed the os furcatorium 

 ov furculum. In the Ostrich the two clavicles are distinct from 



VOL. II. F 



