xm 



PHYLUM CHORDATA 



377 



one another. It is very characteristic of the Bird's skull that 

 the immense size of the eyes has produced a compression of this 

 region of the skull. The ecto-ethmoids or turbinals are compara- 

 tively poorly developed, in correspondence with the small size 

 of the olfactory organs. There are large lacrymals (Fig. 1041, 

 k., Fig. 1042, LCR.), and the nasals (na, na', na", NA) are forked 

 bones, each furnishing both an inner and an outer boundary to 

 the corresponding nostril. 



The premaxillae (p.mx., PMX.) are united into a large triradiate 



PfyJ' * 



EPOT 

 OP.OT 



1 ^ 5gj ,EX.OC 



PROT\ BOC 



^l.pr 



BSPH 

 'MP 



QU 



con 



A. JVC 



AR 



FIG. 1042. Sagittal section of a Bird's skull (diagrammatic). Replacing Bones AL.SPH. 

 alisphenoid ; ART. articular ; B.OC. basi-occipital ; B.SPH. basl-sphenoid ; EP.OT. 

 epiotic ; EX.OC. exoccipital ; M.ETH. mesethmoid ; OP.OT. opisthotlc 

 ORB.SFH. orbito-sphenoid ; PR.OT. pro-otic ; QU. quadrate ; S.OC. supra 

 occipital. Investing bones ANG. angular ; B. TMP. basi-temporal ; COR. coronary 

 DNT. dentary ; FR. frontal; JU. jugal ; LCR. lacrymal ; MX. maxilla; NA. nasal . 

 PA. parietal; PAL. palatine ; PMX. premaxilla ; PT6. pterygoid ; QU.JU. quadrato- 

 jugal ; RST. rostrum; /S. ANG. supra-angular; SPL. splenial ; SQ. squamosal ; VO. 

 vomer ; flc. fos. tloccular fossa ; mx. pal. pr. maxillo-palatine process ; opt. for. optic 

 foramen ; orb. pr. orbital process ; ot. pr. otic process ; pty.fos. pituitary fossa. 



bone which forms practically the whole of the upper beak. The 

 maxillae (mx., MX.), on the other hand, are small, and have their 

 anterior ends produced inwards into spongy maxillo-palatine 

 processes (Fig. 1041, mx.p., Fig. 1042, mx.pal.pr.). The slender 

 posterior end of the maxilla is continued backwards by an equally 

 slender jugal (ju., JU.) and quadrato-jugal (QU. JU.) to the 

 quadrate. The latter (qu., QU.) is a stout, three-rayed bone 

 articulating by two facets on its otic process (ot. pr.} with the roof 

 of the tympanic cavity, sending off an orbital process (orb. pr.) 

 from its anterior margin, and presenting below a condyle for 

 articulation with the mandible ; it is freely movable upon its 

 tympanic articulation, so that the lower jaw has a double joint 

 as in Lizards and Snakes. 



The palatines (pi, PAL.) have their slender anterior ends anky- 

 losed with the maxilla, their scroll-like posterior ends articulating 



