492 MANUAL OF ZOOLOGY SECT. 



the Rabbit, on the other hand, such fusion between elements 

 only takes place in one or two instances, the great majority 

 of the bones remaining distinct throughout life. The lines 

 along which the edges of contiguous bones are united the 

 sutures as they are termed are sometimes straight, some- 

 times wavy, sometimes zig-zagged, serrations of the edges of 

 the two bones interlocking ; in some cases the edges of the 

 bones are bevelled off and the bevelled edges overlap, form- 

 ing what is termed a squamous suture. 



Another conspicuous difference between the skull of the 

 Rabbit and that of the Pigeon is in the mode of connection 

 of the lower jaw, which in the former articulates directly with 

 the skull, the quadrate, through which the union is effected 

 in the Pigeon, being apparently absent. Certain large 

 apertures which are distinguishable are readily identified with 

 the large openings in the skull of the Pigeon. In the pos- 

 terior wall of the skull is a large rounded opening, the 

 foramen magnum, flanked with a pair of smooth rounded 

 elevations or condyles for articulation with the first vertebra : 

 these obviously corresponding to the single condyle situated 

 in the middle below the foramen in the Pigeon. A large 

 opening situated at the end of the snout and looking forwards 

 obviously takes the place of the external nares vi the Pigeon ; 

 and a large opening in the roof of the mouth leading forward 

 to the external nasal opening, plainly represents, though 

 much wider and situated further back, the internal 'or posterior 

 nares of the Pigeon ; while the rounded tubular opening 

 situated at the side of the posterior part of the skull, some 

 distance behind the orbit, is evidently the same as the 

 auditory aperture of the Pigeon. 



Surrounding the large opening of the foramen magnum are 

 the bones of the occipital region of the skull the supra-, ex-, 

 and basi-occipitals. The first of these (s. oc.} is a large plate 



