274 ZOOTOMV. 



front to the septum and free behind, and are ensheathed in 

 the palatine processes of the prernaxillse. The dorsal edge of the 

 septum is produced on each side into a long, narrow, horizontal shelf, 

 which underlies the nasal, and is continued in front into a narrow ali- 

 nasal cartilage, which encircles the nostril and unites ' below with the 

 antero-ventral region of the septum. 



6 1. The parethmoids, or ethmo-turbinals, two 

 complicated folded bones, situated one on either side of the 

 mesethmoid, to which they are ankylosed in the adult. 



62. The vomer, a long bone, deeply grooved on its 

 upper surface, the groove receiving the inferior edge of 

 the lamina perpendicularis and septum nasi ; in the adult 

 it is ankylosed to the parethmoids. 



63. The nasals, two large flat bones which roof in the 

 nasal cavities, articulating with one another in the middle 

 line, and with the frontals behind. The inferior surface of 

 each nasal is produced into a very thin, pouch-like process 

 of bone, the naso-turbinal. 



64. The premaxillse, a pair of irregular bones which 

 form the anterior boundary of the snout. Each gives off a 

 long nasal process from its upper and posterior edge, 

 which passes backwards and slightly upwards, articulating 

 with the external border of the nasal and with the anterior 

 edge of the frontal ; a palatine process from its inner 

 and anterior region, which passes directly backwards, in 

 contact with its fellow of the opposite side along the 

 palate ; and a short, stout maxillary process, which passes 

 directly backwards from its postero-ventral region and 

 articulates with the maxilla in the premaxillo-maxillary 

 suture ; and presents, in its antero-inferior region, two 

 sockets or alveoli for the incisor teeth ( 77). 



65. The maxillae, two large and very irregular bones, 

 which, together with the premaxillse, form the framework of 

 the upper jaw. Their outer surfaces are spongy ; on their 



