388 



ZOOLOGY 



SECT. 



ventrally, in the sagittal plane, into a deep keel or carina sterni 

 (car.), formed, in the young l>ird, from a separate centre of ossifi- 

 cation. The posterior border of the sternum pre?ciits two pairs of 

 notches, covered, in the recent state, by membrane ; its anterior 

 edge bears a pair of deep grooves for the articulation of the 

 coracoids. 



The sktdl (Fig. 1030) 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 ven- 

 tral 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 

 aukylosed in the 

 adult, and can be 

 made out only in the 

 young Bird. 



The occipitals, par- 

 ietals, frontals, and 

 alisphenoids have the 

 usual relations to the 

 brain-case, the basi- 

 occipital (h.o.), as in 

 the Lizard bearing 

 the occipital condyle. 

 The basisphenoid 

 (Fig. 1031, B.SPH), 

 is a large bone form- 

 the greater part 

 the basis cranii 

 and continued for- 

 wards, as in the 

 Lizard, by a slender 

 rodrum (Fig, 1030, 

 pa.s., Fig. 1031, EST.), which represents the anterior portion of the 

 parasphenoid. On the ventral aspect of the basisphenoid paired 

 membrane bones, the had-teniporals (Fig. 1031, B. TMP) are deve- 

 loped, and become firmly ankylosed to it in the adult : they prob- 

 ably represent the posterior portion of the parasphenoid. The 

 tympanic cavity is bounded by the squamosal (Fig. 1030, sq.), 



VCL-S . . 

 r vtfU. 



-Ih.s 

 s.o 

 ejo 



0.C 

 S.dTt CLTl 



Fig. 1030.— Columba livia. Skull of young specimen. A 

 dorsal ; B, ventral ; C, left side. al. «. alisphenoid ; aa. 

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

 exocciijital ; eu. aperture of Eustachian tu1ie ; /'. ra. foramen 

 magnum ;/<■. frontal ; i. o. -y. inter-orbital septum ; jti. jugal ; 

 Ic. lacrynial ; lb. «. lambdoidal suture ; m. ttli. nie.sethmoid ; 

 tii.K. nraxilla ; )((.'■. p. maxillo-palatine process ; na. iia'. aa". 

 nasal ; o.c occipital condyle ; or.fr. orbital plate of frontal ; 

 pa. parietal ; pa s. parasphenoid (rostrum) ; jil. pabitine ; 

 p.m.'-. premaxilla ; pt. pterj-goid ; qu. quadrate; k. an. 

 supra-angular ; s. o. supiaocciijital ; sq. squamosal ; ty. 

 tympanic cavity; II — X 11, foramina for cerebral nerves. 

 (l''roni Parker's Zootoiuy.) 



mo- 

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