TJIE SKELETON OF THE VERTElUtATE HEAD. 147 



the post-frontal process, and may have a branch of conanuni- 

 cation witli the antcro-inferior projection of the mastoid, as in 

 certain parrots. It may also extend down t(j the malar, and 

 may be connected in this direction with the transvei-se pro- 

 jection of the so-called " ethmoid," or pre-sphenoidal centrum. 

 The infra-ocidar bony arch m the maccaws and certain other 

 birds is not a zygomatic arch, although consisting like it of 

 actinapophyseal elements. The proper z}'gomatic arch, as 

 consisting of the malar and squamosal, exists in all birds ; 

 the infra-ocular arch is ossifieil in comparatively few. 



The reference of the lachr}nnal and the other bony forma- 

 tions round the orbit in birds to a mnco-dennal system by 

 the continental anatomists and by Professor Owen, appears to 

 me to be disproved by their relation to the soft parts. They 

 are all developed in aponeurotic bands, which enter into the 

 fonnation of the orbital fascia abeady alluded to. In a band 

 extending along the margin of the sphenoido-frontal, the 

 supra-orliital bone takes its rise, which may thus become con- 

 nected with the lachrymal, when that bone, wliich is developed 

 in the anterior extremity of the band, extends backwards in it. 

 A second band extends downwards and backwards from the 

 lachrymal to the malar, forming a ligament between the two 

 bones, and along which ossification may extend. A third 

 band extends from the post-frontal process downwards and 

 forwards to the quadrate-jugal or squamosal, along which 

 ossification may extend from above. In all birds a baud 

 connects the lachrymo-malar w^ith the post-fronto-squamosal 

 band, thus forming an arch below the under eye-lid. The ex- 

 tension of ossitication into this commissural band, probably 

 from both extremities, completes the infra-orbital bony arch, 

 and may approximate or unite it to the squamoso-jugal or 

 proper zygomatic arch. A fibrous band, which extends down- 

 wards and forwards in the temporal fascia from the anterior 

 process of tlu; mastoid, becomes ossified in some birds ; and 



