Cope.] <^C>4 [April 15, 



being immediately below tliem ; I cannot discover whether there is a 

 posterior one or not owing to injuries to the specimen. There is apparently 

 a fissure-like one on the parieto-squamosal suture posteriorly. The mastoid 

 is quite large, expanding downwards and outwards ; it is not so large as 

 in a tapir, but much exceeds that in Hyrachyus eximius. The meatus au- 

 ditorium exfemus is large, and occupies only the posterior part of the space 

 between the postglenoid and posttympanic processes. It is enclosed an- 

 teriorly and below by the border of a wide element which may be tympanic. 

 It encloses the petrous bone below in a bulla ; as however the inner por- 

 tion of the best preserved one is broken away, I cannot speak of its rela- 

 tions to the basioccipital bone. The foramen lacerum posterius is reduced 

 to a jugular and perhaps another connected foramen by the close apposition 

 of the petrous bone to the basioccipital for a considerable distance. The 

 region of the /. I. medius is injured. Posterior to the /. I. posterius is a 

 foramen opposite the base of the paroccipital process, anterior to the usual 

 position of the /. condyloideum. 



Mandible. The angle of the lower jaw is produced posteriorly, as in some 

 species of Hyracliyus: cfr. figs. Vol. IV, U. S. Geol. Sui*v. Terrs. The coro- 

 noid process is long and is curved backwards to above the posterior border of 

 the condyle. There is no tuberosity behind the condyle. The symphysis 

 is quite contracted and is short. The mental foramen is below the middle 

 of the inferior diastema. The ramus is compressed and at the same time 

 strong. 



Dentition. As the deciduous third and fourth premolar teeth, in a worn 

 condition, remained in the maxillary bone, I removed them from one side, 

 thus displaying the crowns of the corresponding permanent teeth. The 

 first premolar may belong to the permanent dentition ; the second is the 

 deciduous. The former has two roots. The crown is cutting for a short 

 distance anteriorly, but posteriorly it expands into a heel, much less de- 

 veloped than the internal lobe of the succeeding teeth. The crowns of the 

 third and fourth premolars diiier externally, as well as in their crests, from 

 those of the true molars. The median-anterior and cingular vertical ridges 

 are not so prominent as in the latter. The external crest is not divided 

 into two by the notch in its grinding face. The anterior cross-crest, at its 

 inner or distal extremity, is turned shortly backwards and then inwards, 

 giving a "pot-hook" outline to its triturating surface. The fourth de- 

 ciduous premolar presents a peculiar character already ascribed to the first 

 true molar. This consists of a crest running parallel with the posterior 

 transverse crest and close to it, along its posterior side. It forms the 

 border of the tooth for a short distance, but as its direction is slightly 

 obliquely forwards as well as outwards, the posterior cingulum appears for 

 a very short distance. 



The first true molar is subquadrate in outline. The anterior transverse 

 crest commences at the middle anterior ridge, and is first transverse, then 

 directed a little obliquely backwards. The second crest commences at the 

 apex of the posterior external crescent, leaving a wide posterior marginal 



