176 Scientific Proceedings, Royal Dublin Society. 



(3), into whicli a muscle^ is inserted. From the outer surface of 

 the base of the external process (5) a ligament passes to the upper 

 and anterior part of the ethmoid, which is crossed by the palato- 

 premaxillarj ligament externally. Between the two processes is a 

 recess, which slides on the pre-ethmoid cartilage. Below the head 

 is a slightly constricted neck, on the postero-external surface of 

 which is a smooth facet (7) for the end of the palate bone, and 

 below this, on the posterior border, the posterior maxillo-mandi- 

 bular ligament is attached. This passes to the outer side of the 

 08 articulare, just in front of the articular cavity, of the mandible. 

 From the anterior angle of the lower end (9) the anterior maxillo- 

 mandibular ligament passes to the outer side of the dentary, near 

 the symphysis menti. 



The mandible consists of three bones — articular, dentary, and 

 angular.^ 



The articular presents, on its upper surface posteriorly, an arti- 

 cular cavity for the quadrate, which is concave from before back- 

 wards, and slightly convex from side to side. In. front of this the 

 bone spreads out into a thin triangular plate. Below and in front 

 of the articular cavity, a process stretches downwards and forwards, 

 forming an angle with the rest of the bone, into which part of the 

 dentary fits externally. Internally, between this process and a 

 ridge which stretches downwards from the back part of the arti 

 cular cavity, is a deep groove, into which the angular fits; Below 

 the triangular plate is a strong ridge, the lower border of which 

 joins edge to edge with a ridge which runs along the middle of 

 the dentary. On the inner surface of the ridge, near its posterior 

 end, is a projecting tubercle, into which the tendon of the tem- 

 poral muscle is inserted. From this tubercle a persistent rod of 

 cartilage (Meckel's) extends forwards, lying above and internal to 

 the ridge (which supports it), and, with the anterior extremity of the 

 above-mentioned triangular plate, fits into the hollow of the dentary. 



The denlary bears teeth' on its upper surface (which opposes 

 the premaxilla). The teeth are all small and curved, the points 

 being bent towards the cavity of the moutii. On the premaxilla 

 there are about eight rows, of twenty to thirty in a row. The 



^ Eegarded as the analogue of the masseter by Cuvier. (See PI. VII., fig. 13.) 

 - 1 have looked in vain for a splenial ossification. 



