WILLISTON: RESTORATION OF PLATYGONUS. 29 



The palate is somewhat more deeply concave in front, and more 

 roughened on the side. Posteriorly, in place of the fossa, which is 

 narrowed posteriorly into a slender grove in Dicotyles, there is an 

 acclivity ending in a shallow, broad groove, which soon becomes 

 steep to the margin of the posterior nares, which are situated much 

 higher up. The pterygoid plate, instead of contracting so that the 

 small pterygoid processes are nearly in contact, pass nearly straight 

 backwards, and a little outward to the tympanic bullie. They do 

 not have a reflected margin posteriorly, and the notch for the carotid 

 foramen is smaller. The result is that the inferior opening for the 

 nares is not cordiform, but is elongate, much broader and much 

 deeper. The sphenoid turns upvvard, almost at a right angle with 

 the basilar process, which has at its anterior angles prominent tuber- 

 osities. The tympanic bullae are nearly as in Dicotyles, but the 

 basioccipital' between them is nearly horizontal, and the glenoid pro- 

 cesses are turned obliquely outward and forward, with the articular 

 surface further below their level. The paroccipital processes are a 

 little longer, and the condyles are placed more below the plane of the 

 buUoe. Just in front of the condyles there is a much deeper depres- 

 sion on each side of the middle. The glenoid surfaces are less elon- 

 gate, and directed more antero-posteriorly. The post-glenoid pro- 

 cesses do not differ, but are located further out from the antero- 

 posterior line of the molars. The foramen magnum is more oval, 

 the occipital surface steeper. The diastema between the premolars 

 and the canines is much longer in Platygonus, being equal to nearly 

 two-thirds of the length of the cheek teeth, while in Dicotylcs it is not 

 more than one-third of the length. The distance between the canines 

 is proportionally greater, while the proportion of the face in front of 

 the canines is much smaller. The incisors are much smaller, espe- 

 cially the outer one, which is feebly developed. The anterior palatine 

 foramina, situated almost wholly within the premaxillse, are smaller. 

 The lateral borders of the premaxillse above are broader and more 

 divergent, and the superior process extends backward nearly as far as 

 the first premolar tooth. The anterior nasal opening is more trans- 

 verse, and more open, narrowed above, with the lateral vacuity 

 reaching farther back, as far as the top of the canine tuberosity. The 

 nasals on the distal half are not convex above transversely, or gently 

 flattened, but have a distinct, shallow groove; they terminate in front 

 in an elongate narrow process, and not almost in a right angle, as in 

 Dicotyles. They are more elongate, tapering gradually from their 

 origin, and are less convex on the upper part. The groove on the 

 sides is about as it is in Dicotyles, the foramen in which it terminates 

 being about opposite the fronto-nasal suture. The frontal and ante- 



