Skull of Fowl. 



99 



which, as in the frog, enter into the formation of the skull wall. 

 The first arch, the mandibular, is formed out of the quadrate 

 {g), above, a roughly triradiate bone. Below there is, in the 

 young fowl, Meckel's cartilage, which is surrounded by a set of 

 membrane bones which form the actual lower jaw of the adult ; 

 but the proximal end of the Meckel's cartilage is ossified to 

 form the articulare (a.i) — that portion, in fact, which articulates 

 with the quadrate. There is, however, no Mento-meckelian.^ 

 The membrane bones which ensheath the rest of Meckel's 



Fig. 43. — Diagram of Bird's slcull. (Mainly after Gadow.) 



C^tilage bones (white): b.oc, basi-occipital ; i.oc, ex-occipital; s.oc. supra-occipital; 

 ' PER, periotic (behind it is columella): QR, quadrate: b.sph, basi-sphenoid ; alsp, 

 ~ ali-sphenoid ; pr.sph, pre-sphenoid ; or.sph, orbito-sphenoid ; turb, turbinals ; eth, 

 prefrontal; sept, ethmoidal septum; art, articulare; CER.BR, UR.HY, hyoid bones. 

 Membrane bones (dotted) : PR, parietal ; SQ% squamosal ; FR, frontal ; above 

 turbinal is lacrymal (not lettered): NA, nasal ; PMX, premaxilla ; vo, vomer; MAX, 

 maxilla ; PAL, palatine ; PTY, pterygoid : B.T, basi-temporal ; JUG, jugal ; qr, quadrato- 

 jugal ; DENT, dentary ; SPL, splenial ; ang, angulare ; s. ang, supra-angulare. 



cartilage are denfary (d), angular (a), supra-angular (s.a), and 

 splenial. 



The second arch is formed above by the columella, a rod- 

 like bone, which is — as in the frog — associated with the 

 auditory organ. The Ayoid bone lies in the tongue, and consists 

 of a basal piece and of two lateral outgrowths; of these the 



hawk. 



A Mento-meckelian ossification has, however, been discovered in a 



