OSSEOUS SYSTEM OF AVES. 47 



of the under and outer part of the anterior production of the 

 notochordal capsule. In the young Ostrich the presphenoidal 

 rostrum intervenes between the vomer^ is, and prefrontals, 14. 

 These latter bones manifest the essential neurapophysial rela- 

 tions to the rhinencephalon and olfactory nerves : but they early 

 coalesce together and with the rhinal capsules, as in the tail- 

 less Batrachians. The anterior contraction of the cranial cavity, 

 which affects the orbito-sphenoids, influences still more the pre- 

 frontals, and, in connection with the large relative size of the eye- 

 capsules, becomes the condition of the extreme modification of the 

 neurapophyses of the foremost cranial vertebra. The neural spine 

 (nasals), 15, is divided along the middle line; but in most Birds 

 the suture becomes obliterated and the spine coalesces with its 

 neurapophyses, with the frontal spine, and with those parts of the 

 hasmal arch of the nasal vertebra with which it comes in contact. 



The pleurapophyses (palatines), 20, of this inverted arch retain 

 their typical connections with the nasal centrum and neurapophy- 

 ses at one end, and with the haimapophysis (maxillary), 21, at the 

 other end, and they also support the constant element of the di- 

 verging appendage of the arch (pterygoid), 24. The ha3mapophy- 

 sis (maxillary), 21, resumes in birds more of its normal proportions 

 and elongated slender form, as such : but the haemal spine (premaxil- 

 lary), 22, is largely developed though undivided, and sends upward 

 and backward from the part corresponding to the symphysis of 

 the spine, a long pointed process, 22', which joins and usually 

 coalesces with the neural spine, 15, and divides the anterior outlet 

 of the haimal canal into two apertures called the nostrils. The 

 modification of the haemal arch of the nasal vertebra in the Lizard 

 tribe is here repeated. The pleurapophysial appendage (pterygoid), 

 24, connects the palato-maxillary arch with the tympanic, and in 

 the Ostrich and some other birds, also with the basisphenoid, 5, 

 and fig. 27,/: the second or ha3mapophysial ray of the diverging 

 appendage (malar and squamosal) is developed in all Birds, as in 

 the squamate Saurians, combining the movements of the haiinal 

 arch of the nasal vertebra with that of the frontal vertebra, and 

 consisting of the two styliform ossicles (malar, 20, and squamosal, 

 27), which extend from the ha^mapophysis, fig. 28, 21, 21'', to the 

 pleurapophysis, 28 : the essential relationship of the compound 

 ray, 26 and 2:, with the nasal vertebra, is indicated by their 

 becoming confluent with its hiismapophysis, at 21'', whilst they 

 maintain an arthrodial articulation ^vith the pleurapophysis, 2s, of 

 the succeedinoj vertebra. 



The bones of the splauchno-skeleton intercalated with ihc 



