COLUMBA. 369 
the special points to notice are as follows:—(1) The 
cerebral hemispheres are large and reach the 
cerebellum posteriorly, hence the optic lobes 
are /ateral in position. (2) The whole of the brain lies 
behind a line drawn through the eyes. (3) The olfactory 
lobes are very small and poorly developed. 
The skeleton of the pigeon is as remarkably 
modified as is the rest of its anatomy. ° 
In the skull we may note the complete fusion of the 
cranial and some of the facial bones, leaving no sutures. 
The upper beak is supported chiefly by the premaxille and 
by the maxi//e, the thin juga/ joining the maxille with the 
quadrate posteriorly. Further, towards the middle ventral 
line the two fadatines pass back from the maxille to meet 
the perygoids which pass outwards and backwards to join the 
Nervous. 
Skeletal. 
Fig. 261.—A CERVICAL VERTEBRA OF THE PIGEON. (4d nat.) 
Neural Crest. 
Neural Canal. 
\ Vertebrarterial 
anal. 
Cervical Rib. 
Heteroccelous Facet. 
guadrates. ach quadrate has a condyle for articulation with 
the mandible bearing the lower beak ; they are freely movable 
upon the skull. All the other bones are fused. 
The orbits are very large and are separated by a thin 
septum only partially ossified, the zxéerorbital septum. Its 
ventral edge, under the palatopterygoid junction, is thick- 
ened and forms the rostrum. 
The septum is said to be formed of the mesethmoid and presphenoid 
of the rabbit, whilst the rostrum is supposed to be homologous with the 
anterior part of the frog’s parasphenoid, the posterior part of which is 
represented by the paired dasztemforals ventral to the dasisphenoid. 
There are three ear-bones but the fro-ot/c alone remains free, the 
others fusing with the occipital bones. 
There is a single occipital condyle on the basisphenoid 
and the mandible is ossified into five bones. 
M, 25 
