Oligocene (White River) F elides. 213 



The skull resembles that of H. primcevus Leidy in 

 some characters and that of i?. oreodontis Cope ^ in 

 others, but it has several distinctive features of specific 

 value, the most prominent of which are the very large 

 incisor alveoli, the long sharp-pointed palate, the pe- 

 culiar shape of the canines, and the very large molar 

 alveoli. 



The basal length of the skull is 147 mm., which is 

 next to that of the smallest species of the genus, but 

 the incisors, measured at the alveoli, are proportionately 

 much larger, their dimensions being as follows : 



anteroposterior transverse 



I 1 7 mm. 4.5 mm. 



I 2 7 mm. 4.75 mm. 



I 3 8 mm. 5.5 mm. 



Anterior to the orbits, the face is flat, but in front of 

 the infraorbital foramen the maxillary is strongly con- 

 vex, due to the alveolus of the canine. The infraorbital 

 foramina are large and subangular. The diastema be- 

 tween I 3 and the canine is proportionally a little longer 

 than in H. primcevus Leidy. The palate is nearly 20 per 

 cent longer than in H. oreodontis Cope. The premaxil- 

 lary border is very convex anterior to the line of the 

 canines. It is, in fact, so pointed that it is unlike any 

 other species of Hoplophoneus. The canines are de- 

 cidedly laterally compressed. The maximum diameter 

 at the alveolus is 14.5 mm., and the transverse diameter 

 is 5.4 mm.; or the maximum diameter is nearly three 

 times the transverse, whereas the other species gener- 

 ally show a relation of about twice the maximum over 

 the transverse. The posterior cutting edge or axis of 

 the canine is at right angles to the plane of the palate. 



Cope, in describing H. oreodontis, stated that there 

 was no indication of the existence of a second premolar, 

 but one is present on the left side of this specimen, al- 

 though there is none on the right. This P 2 had insufficient 

 space to develop between the canine and P 3 and hence 

 its position is inward from the true line of the teeth. 

 The diastema between the canine and P 3 on the left side 

 is nearly equal to that between the canine and the I 3 . The 

 posterior edge of the paracone of P 3 is denticulate. The 

 total length of the tooth row is 54 mm., which makes it 

 appear near to II. oreodontis in size, but this is due to 



