SKULL 



403 



formed mainly by the basioccipital. In front of the basioccipital 

 is the basisphenoid, and above this on each side the wall of the 

 cranium is partially formed of 

 an alisphenoid. The front of the 

 cranium, and the interorbital 

 septum, consist of a single bone 

 representing mesethmoid, pre- 

 sphenoid, and orbitosphenoids. 

 The remainder of the cranium 

 is formed of membrane bones ; 

 parietals and frontals in the roof 

 and small lacrimals in front of 

 and above the orbits. Below the 

 basiphenoid is a pair of bones 

 sometimes called basitemporals, 

 which represent the posterior 

 part of the parasphenoid of the 

 frog, and a piece of membrane 

 bone representing the front end 

 of this is fused on to the inter- 

 orbital septum to form the rost- 

 rum. The basitemporals and the 

 rostrum all become fused to 

 the basisphenoid. The auditory 

 capsule consists of a single peri- 

 otic below the parietal, and in 

 front of the capsule a squamosal 

 completes the covering of the 



/X, AV 



XIL 



f. m. 



Fig. 317. — The skull of a pigeon, seen 

 from below. 



ht., Basitemporal ; Eu., hinder opening of passage 

 for Eustachian tube ; Eu'., anterior opening 

 of the same ; f.m., foramen magnum ; m., 

 maxilla ; mp., maxillopalatine process ; o.c, 

 occipital condyle ; pL, palatine ; pm., pre- 

 maxilla ; pt., pterygoid ,q., quadrate ; q.j., 

 quadratojugal ; rs., rostrum ; IX., X., XII., 

 foramina for cranial nerves. 



£0c 



Fig. 318. A diagram of a bird's skull, disarticulated. — After Gadow. Membrane 



bones shaded. 



B.Oc , Basioccipital; E.Oc, exoccipital ; S.Oc, supraoccipital ; Pa., parietal; Fr., frontal; Na., nasal; 

 pm., premaxilla; M., maxilla; Jti., jugal ; Qj., quadrato-jugal ; Qii., quadrate; PL, palatine; Pt 

 pterygoid ; pe., periotic ; Sq., squamosal ; AS., ahsphenoid ; B.S., basisphenoid ; O.b., orbitosphenoid ; 

 Pr Sph , presphenoid ; vo., vomer ; iOS., interorbital septum ; £., ethmoid ; Se., nasal septum ; De., 

 dentary ; Sp., splenial ; An., angular ; S.A., supra-angular ; Ar., articular ; MK., Meckel's cartilage ; 

 Tu., cartilaginous turbinal. 



