376 



ZOOLOGY 



SECT. 



p.mx 



The skull (Fig. 1041) is distinguished at once by its rounded 

 brain-case, immense orbits, and long, pointed beak. The foramen 

 magnum (f.m.) looks downwards as well as backwards, so as to be 

 visible in a ventral view, and on its anterior margin is a single, 

 small, rounded occipital condyle (o.c.). Most of the bones, both of 

 the cranial and facial regions, are firmly ankylosed in the adult, 



and can be made out 

 only in the young 

 Bird. 



The occipitals, 

 parietals, frontals, and 

 alisphenoids have^ the 

 usual relations to the 

 brain-case, the basi- 

 occipital (b.o. ), as in 

 the Lizard, bearing 

 the occipital condyle. 

 The basisphenoid 

 (Fig. .1042, B.SPH.) 

 is a large bone form- 

 ing the greater part of 

 the basis cranii and 

 continued forwards, 

 as in the Lizard, by a 

 slender rostrum (Fig. 

 1041, pa.s., Fig. 1042, 

 RST.), which repre- 

 sents the anterior por- 

 tion of the para- 

 sphenoid. On the 



FIG. 1041. Columba livia. Skull of young specimen. Ventral aspect of the 



A, dorsal ; B, ventral ; C, left side. al.s. alisphenoid ; an. basisphenoid paired 

 angular ; ar. articular ; b. o. basi-occipital ; d. dentary ; , 



e. o. exoccipital ; eu. aperture of Eustachian tube ; /. m. membrane DOneS, tile 



foramen magnum ;fr. frontal ; i. o. s. inter-orbital septum ; 7 t ann ^ nnf , nff1 'l /T7 ; 



ju. jugal ; Ic. lacrymal ; Ib. 8. lambdoidal suture ; m. eth. OaSl-tempOmiS (V 1 g. 



mesethmoid ; mx. maxilla ; mx.p. maxillo-palatine process ; 1 (UO R TMP\ are 



na. no,', na". nasal ; o.c. occipital condyle ; or.fr. orbital J 



plate of frontal ; pa. parietal ; pa.s. parasphenoid (roatrum) ; developed, and become 



pi. palatine ; p.mx. premaxilla ; pt. pterygoid ; qu. quadrate ; , J , , -, 



s. an. supra-angular ; s. o. supra-occipital ; sq. squamosal ; nrmly anKyiOSCQ DO ID 



ty. tympanic cavity; // XII, foramina for cerebral J.T^ Qr lnlf f>>oTr 

 nerves. (From Parker's Zootomy.) 



J.T^ Qr lnlf 

 m tne adult . 



probably represent the 

 posterior portion of the parasphenoid. The tympanic cavity is 

 bounded by the squamosal (Fig. 1041, sq.), which is firmly united to 

 the other cranial bones. The main part of the auditory capsule is 

 ossified by a large pro-otic (Fig. 1042, PR.OT.) : the small opisthotic 

 of the embryo early unites with the exoccipital, the epiotic with 

 the supra-occipital. The parasphenoid and mesethmoid together 

 form the inter-orbital septum (Fig. 1041, i.o.s.), a vertical partition, 

 partly bony, partly cartilaginous, which separates the orbits from 



