Professor H. G. Seeley — Dentition of Cynognathiis. 489 



cutting-edge in front, and is rather larger than the second. The third 

 is longitudinally oval, and the fourth and fifth are more elongated, 

 with a laterally compressed aspect. All are crowded into close contact. 



The fracture passes through the root of the sixth tooth, which is an 

 inch deep in the jaw, and shows the anterior border of a pulp cavity, 

 which appears to be narrow, but is closed at the base. The root is 

 "iV inch wide, slightly curved inward, and its termination shows 

 a slight notch, too slight to suggest root tubercles. 



The palatal surface (PL XXIV, Fig. 1") comprises three areas: 

 first, the external dentigerous border described ; secondly, a middle 

 smooth longitudinal channel ; and thirdly, an inner longitudinal dental 

 armature. 



The middle concavity is wide and inclined on the outer part, narrow 

 and steep towards the inner teeth. The more flattened part is marked 

 towards the alveolar border with a fine, impressed, longitudinal, vascular 

 line almost like a suture, but there is no trace of sutural separation 

 on the posterior fracture. This smooth area ascends in front of the 

 canine tooth into the pit for the mandibular canine, by a continuous 

 rounded surface. The mandibular canine pit is apparently triangular, 

 1 J inch deep, convex over the inner side of the canine, concave on the 

 external lateral border, and internally it is obscured a little towards 

 the palatal armature by crushing, but was probably concave. 



The smooth palatal surface is about f inch wide behind the canine 

 tooth where widest, and extends backward with a uniform width of 

 about half an inch. Opposite the fourth and fifth molars it develops 

 a small longitudinal ridge, and on the inner side, next the palatal 

 armature, there is a deep narrow groove, which is prolonged upward 

 as a cleft or canal as though the palatal plate of the maxillary had 

 originally been a distinct ossification from the dentary plate. 



The internal portion of the palate, which carries a dental armature 

 adapted for crushing food, is wedge-shaped in form, narrow in front 

 between the canine teeth, widening posteriorly to fully half an inch at 

 the posterior fracture. On the inner margin it forms a strong dental 

 ridge, but the rest of the plate is inclined outward, so that its thick- 

 ness diminishes towards the smooth channel already referred to. This 

 armature has a certain resemblance to the tooth-plates of Hyperodapedon 

 carried upon the maxillary bones and upon the parallel palatine bones. 

 But these tooth-plates are supported upon the maxillary bone only, 

 like the separate teeth of Endothiodonts and Lycosaurians. This 

 triangular dental wedge is a little injured by transverse fractures, 

 made during movements of the rock, which have bent it slightly 

 outward at both the anterior and posterior ends. The tooth-plates are 

 supported upon a very thin palatal expansion of the maxillary bone. 

 With this the crushing toothed armature unites without visible suture. 

 But a small dental plate anterior to the others was not anchylosed, 

 and is lost. Its empty socket (PI. XXIV, Fig. 1, E.S.) next the 

 vacuity for the mandibular canine tooth shows that it had a basal 

 and internal support, and rested against the dental plate behind. The 

 premaxillary bones may have extended between and above this region 

 of the armature, but there is no evidence of those bones preserved, 

 unless it be in the anterior internal thickening of the maxillary bone 



