3i6 SCOTT. [Vol. XL 



size ; they project but little in advance of the canines and so 

 do not add much to the length of the muzzle. The alveolar 

 portion forms a thin, depressed, and delicate plate, with regu- 

 larly rounded free margin, which in shape resembles that of 

 Cariaciis. The spines, on the other hand, are relatively quite 

 broad and very thin, and hence the incisive foramina form 

 narrow crescentic slits, the outer wall of which is formed for 

 nearly half their length by the maxillaries ; these foramina are 

 thus much less widely opened than in most ruminants, which 

 is due to the narrowness of the spines in the latter. The 

 ascending ramus of the premaxillary is short and slender and 

 forms an obtuse angle with the alveolar portion ; it is separated 

 by nearly half the length of the skull from the shortened nasal. 

 In the saiga the premaxillaries are much heavier and wider 

 proportionately than in Protoceras and the ascending portion 

 makes a still more open angle with the alveolar portion ; in 

 Hydropotes the ascending ramus is wider. 



The maxillaries have considerable resemblance, when seen 

 in profile, to those of the saiga antelope, but owing to the 

 extremely brachyodont dentition, the alveolar portion is much 

 lower, and as the orbit is considerably less elevated above the 

 level of the palate, the descent of the upper or free margin of 

 the maxillaries toward the front is much more gradual. An- 

 other difference between the two genera consists in the more 

 complete reduction of the nasals in the modern type and the 

 larger size of the lachrymals, owing to which the latter form 

 the upper margin of the nasal chamber for some distance. In 

 Protoceras the nasals articulate with the maxillaries and thus 

 cut off the lachrymals from the border of the nasal chamber. 

 The vertical plate of the maxillary above the sinus or antrum 

 is very thin and delicate, but has a round, seam-like free border, 

 which is a little thicker than the rest of the plate. As Osborn 

 and Wortman conjectured, there are no such great and massive 

 protuberances on the maxillaries as occur in the male, but they 

 are faintly indicated by a slight upward arching of the border ; 

 posterior to this the margin is notched and from the notch 

 descends a shallow groove, doubtless marking the course of a 

 blood-vessel. The masseteric ridge is very prominent, though 



