138 Annals of the Carnegie Museum. 



form. P."^ has )iot yet developed the two distinct transverse crests so 

 characteristic of all previously known Acerafheres afid Rhinoceroses. 

 All the premolars show a rather large postfossette and a small prefos- 

 sette opening into a larger medifossette entirely enclosed internally. 

 There is a small crista on each, separating the prefossette from the 

 medifossette, while the ectoloph of each supports an anterior and pos- 

 terior costa and a rudimentary parastyle. Internal cingula are present 

 on P.^, ^, i. I wish here to call attention to the apparent difference 

 in the structure of P. A on opposite sides, due to different degrees of 

 wear exhibited by these teeth in the same skull as shown in Plate II., 

 Fig. 2. In M.J- the median sinus is well developed, completely sepa- 

 rating the protocone and hypocone. The ectoloph supports a well 

 developed parastyle, separated from the anterior costa by a well marked 

 fold. The posterior costa is faint. This tooth is much worn, but 

 remnants of the post- and medifossettes remain. M.-3- is the larger 

 tooth of the series ; the protocone is more prominent than the hypo- 

 cone ; there is a postfossette and a medifossette invaded by an ante- 

 crochet. The ectoloph supports a well developed parastyle and ante- 

 rior costa, with scarcely an indication of the posterior costa. In M.-^- 

 the metacone is absent, while the protocone, paracone and hypocone, 

 are well developed. There is a deep medifossette unobstructed by 

 either crochet, antecrochet, or crista. There is a parastyle and a 

 strong anterior costa. All the superior molars bear anterior and pos- 

 terior basal cingula. 



The inferior dentition : The first pair of lower incisors are small 

 spatulate teeth with the longer axis directed transversely. They are 

 remarkably procumbent and are placed anterior to and between the 

 second pair of incisors, which have become hypertrophied into large 

 procumbent teeth, which in the rhinoceroses generally, have been 

 usually mistaken for canines rather than incisors. Just below their 

 crowns these teeth are oval iij cross-section. Immediately behind 

 1.2^ there is a shallow alveolus, which with Lucas, I have assigned to 

 I.^ rather than the canine. Whether it was occupied by the canine 

 or I.^ is of minor importance, — in either case it fixes the large pro- 

 cumbent tooth as a modified incisor, as was pointed out by Lucas in 

 his original description of the genus. I. ^^ is separated from P.y by a 

 long diastema. P.y is a small, laterally compressed tooth, fixed in 

 the jaw by two roots, and bearing on its crown anterior, median, and 

 posterior cones arranged longitudinally, with but faint indications of 



