132 ME. W. K. PAEKER ON THE STEUCTUEE AND 



there is a thick cushion of dense fibrous tissue. The only part of these cartilaginous 

 folds which ossifies is the pars plana ; there is one centre for the inner part which 

 walls in the end of the inferior turbinal scroll, and which runs upwards towards the 

 olfactory crus ; and another for the plaited part which sends inwards the middle turbinal 

 outgrowth (Zoological Transactions, vol. v. plate 42, fig. 4, ao. 1, ao. 2). Already the 

 prenasal rostrum is diminishing in size, afterwards it will vanish, and with it a goodly 

 territory of the septum between the alse nasi ; thus two cartilaginous, and one actually 

 ossified tract, disappear by the time the bird is fuU-grovvm. Mere connective fibre is left 

 in these absorbed regions. Three tracts of unossified cartilage are seen in a section of 

 the ethmoid in the ripe young ; the upper is the core of the upper bone, the middle 

 is above the junction of the two vertical lamellse, and below the coalescence of the 

 upper and lower bone ; the lowest tract is between the vertical lamellse, and is con- 

 tinuous with the unchanged trabecular region (Plate X. fig. 13). 1 have already shown 

 that the prenasal rod (])n.), formed by the coalescence of the anterior horns of the tra- 

 beculee, is really the proper axis of the intermaxillary apparatus ; the primordial part of 

 the palatine arch behaves differently. As in Struthio, the palatines and pterygoids 

 (Plate IX. figs. 1,2 & 4, pct.pg.) ossify whilst the tissue is in a simply cellular con- 

 dition ; the pterygoids are like those of the Ostrich-tribe, but the palatines show scarcely 

 any of the anterior bar, and thus differ very much not only from ordinary birds, but also 

 from the Great Ostrich. Indeed the whole bar is almost divided obliquely from end to 

 end to form the pterygoid and palatine, the former being broad behind and sharp in 

 front, and the latter narrow and broad in the contrary direction ; the inner edge of the 

 broad deeply-toothed anterior end of the palatine is the suspensory part of this arcade, 

 the axis of the pterygo-palatine apparatus*. The triradiate, massive, quadrate cartilage 

 (Plate IX. q.) is still unossified at the end of its metapterygoid process, and at the upper 

 and lower articular surfaces ; the former is a continuous oblong condyle, as in all the 

 congeners of this genus. The "articulare" (Plate IX. figs 2 & 3, ar.) has begun to 

 form in the thick malleal head of Meckel's cartilage ; its first lamella appears in the 

 flat posterior face, which ends inwards in the clubbed internal angular (manubrial) pro- 

 cess ; all the rest of the primordial part of the mandible is still cartilaginous (Plate IX. 

 fig. 2, mk.), anteriorly it has begun to shrink. The main part of the auditory columella 

 (Plate IX. fig. 3, st.) (stapes) has ossified, the cartilaginous part is triple; one flat bar 

 in a line with the bony rod, a long terete branch, running forwards at right angles to 

 the stem, and a smaller similar rod going directly backwards. This is the detached 

 suspensory part of the hyoid arch; the disjoined rami and base are, together, elegantly 

 arrow-shaped (Plate IX. fig. 7, c.h.b.h.), for each flat cerato-hyal cartilage has joined its 

 fellow at the mid line, forming a point anteriorly, whilst each ramus passes backwards 

 free and pointed. The basihyal is very pointed in front where it fits into the acute angle 

 formed by the meeting of the flat oornua ; it has no uro-hyal prolongation, the thyro- 



* Only the pier of the palato-pterygoid arch is ever developed in the Vertebrata generally ; there is no seg- 

 mented descending rod. 



