gg THE MERYCOIDODONTID^ 



Mandible: The symphysis is strongly fused, and the profile of the chin is nearly straight, with 

 the symphysiodental angle 45 J . The mental tubercle is not great. The horizontal ramus is 

 stout, with a nearly straight inferior border and the angle barely descending below that border. 

 The ascending ramus is anteroposteriorly wide and has a deep masseteric fossa. The condyle is set 

 well forward from the posterior border of the ramus, and it is decidedly convex. The sigmoid notch 

 is small, and the small, thin coronoid process does not extend far above the level of the condyle. 



Foramina: The infraorbitals lie above the middle of P 3 . The supraorbitals are 13 mm. apart 

 and close to the sagittal suture. The posterior palatine foramina are opposite the posterior of P\ 

 The tympanohyal pit is deep, and the stylomastoid foramen is situated externoposteriorly to it. 

 These foramina are separated by a thin ridge of bone, and the stylomastoid is much smaller than the 

 tympanohyal. The opening of the stylomastoid is a groove rather than a pit. There is a deep pit for 

 the postglenoid foramen. The condylar foramen and the foramen lacerum fosterius are in their 

 normal position. The carotid canal is very small, while the foramen lacerum medium is large and 

 located slightly anterointernally to the bulla. The foramen ovale is small and lies just anterior to 

 the bulla. The foramen lacerum anterius (sphenoidal fissure) is relatively large. The foramen 

 rotundum is absent. 



Dentition: The molar-premolar index of the superior series is 0.88 and that of the inferior 

 series 0.85. The inferior canine is about twice the size of the third incisor and has incisiform char- 

 acteristics. The inferior incisors extend obliquely upward and forward, while the superior ones 

 extend slightly forward and downward, with their crowns pointing wholly downward. The shape of 

 the superior ones is that of an ovoid, convex externally and excavated internally, with sharp edges, 

 while that of the inferior incisors is more like a trapezoid, with nearly flat external outer surfaces 

 and convex inner ones. The superior canine curves slightly backward and outward, but strongly 

 downward. Its shape is trilateral, sharp-pointed, with its sides nearly equal and almost straight. 

 One side is set transversely to the sagittal plane. The inner face has a deep median groove, starting 

 at the base of the crown and gradually dying out downward. Pi is directed forward, outward, and 

 upward. It is placed obliquely in the jaw, strongly convex on its outward face and but slightly 

 convex inwardly. It is laterally compressed, and its edges are acute. Both upper and lower func- 

 tional canines are of about the same length but of different shape in each set. The superior canine 

 is separated from the first premolar by a short diastema. 



The upper premolars increase successively in size from first to fourth. The anterior three are 

 of the same pattern — oblong in basal outline, medially divided in an anteroposterior direction by an 

 acute ridge, terminating in an apex. An internal medial transverse ridge joins the apex with the 

 base of the crown. The external face is slightly convex, and the internal is excavated on each side 

 of the median transverse ridge, the posterior excavation being the larger. The posterior transverse 

 diameter is greater than the anterior in all of these three superior premolars. In these same teeth 

 the anterointernal excavation is divided anteriorly by a short ridge connecting the main fore and aft 

 ridge and the cingulum, forming a very small anterior pit above the cingulum. The fourth pre- 

 molar consists of two transversely placed crescent-shaped demiconoidal lobes very similar to the 

 molars but relatively larger. The outer face is concave, divided by a very slight ridge. 



The second and third lower premolars are obliquely placed in the mandible, compressed oval 

 shaped, with an anteroposterior acute median ridge terminating in an apex. A median internal ridge 

 connects the apex and cingulum. This ridge is not transverse to the main one but forms an acute 

 angle posteriorly, surrounding a shallow fossa. The anterior fossa is shallower and larger. The 

 fourth premolar is more oblong shaped, and the internal median ridge is situated nearly at right 

 angles to the anteroposterior one. Its internal border is approximately as high as the main apex, 

 thus forming a deep pit in the posterointernal part of the tooth and a deep concavity on the antero- 

 internal part. 



The true molars in both series increase in size from first to last and consist of four crescent-shaped 

 demiconoidal lobes. The superior molars are nearly square, while the inferior are slightly greater 

 anteroposteriorly, except M 3 , which has a much greater length in the anteroposterior diameter. 



