BY C. D. GILLIES AND EDNA F. PEBERDY. 119 



-curve outwards, and their outer edges project slightly over 

 the sphenethmoid. In the postero-lateral walls of the 

 latter are the paired foramina for the entrance of the 

 ophthalmic branches of the trigeminal into the olfactory 

 capsules (fig. II, V.,). Attached to the antero- ventral 

 surface of the sphenethmoid are the vomers (fig. II, vo.) 

 which diverge anteriorly placing their distal extremities 

 into relation with the premaxillo- maxillary junctions. 

 Each consists of a curved bar with a thin pointed lamina 

 arising from its outer border ; the posterior region of the bar 

 bearing the teeth is thickened (fig. II, vo.t.) and along the 

 inner aspect of the vomer is a groove which fits into the 

 sphenethmoid. 



(6) The Maxillary Arch. 



As the following bones are paired and symmetrically 

 ■arranged, only one side need be described. 



The premaxilla (fig. II, p.m.) is triradiate the rami 

 being — 



I. Antero-dorsal (fig. I, a.d.r.) dorsall}- directed and 



arising near the s^miphysis. 



II. Maxillary (fig. I, m.r.) running postero-laterally 

 to the maxilla and bearing teeth like the latter. 



III. Posterior (fig. II, jJ.r.). This ramus has its 

 origin near the antero-dorsal, and forms a prom- 

 inent tooth-like process immediately within the 

 anterior extremity of the upper jaw. 



The maxilla (m.) has a nasal process (fig. I, tia.p.), 

 which is connected with the nasal. In front of the latter 

 the maxilla is lateral^ compressed, while behind it gradually 

 tapers to a point. Above the teeth of the premaxilla and 

 maxilla is a small but definite flange of bone. The teeth 

 of the maxilla extend a short distance behind the maxiilo- 

 pterygoidal junction (fig. II, m.pt.j). The siDhenethmoidal 

 attachment of the palatine (fig. II. pal.) is posterior to the 

 vomer, while the maxillary connection is in the region of 

 the nasal process. On the inner side of the posterior 

 portion of the quadrato-jugal (fig. II, q.j.) is ankylosed 

 the quadrate (fig. II, q.), the dual ossification having the 

 shape of a hammer lying on its side. The long ramus of 



