PETERSON: THE AMERICAN DICERATHERES. 



407 



Contour of Skull compared with the Dentition.— Confinwed. 



Contour of Skull. 



Dentition. 



D. No. 2467. 

 female. 



Fullv adult 



E. No. 1855. Paratype of 

 D. cooki. Female. 



F. No. 2809. Male. 



Skull somewhat crushed back- 

 ward and to one side, though of 

 quite symmetrical appearance. 



Only a suggestion of horn-cores, 

 nasals not projecting over the pre- 

 maxillaries, quite long and pointed 

 in front of the horn-cores and very 

 little constricted back of them; 

 frontals quite broad, though slightly 

 injured by lateral crushing; tem- 

 poral ridges prominent, and remain- 

 ing well apart throughout to the oc- 

 cipital crest; brain-ca.se large, zygo- 

 matic arches light. Skull propor- 

 tionallv high and narrow. 



Skull somewhat crushed to one 

 side. 



Nasals broken well back, but the 

 sides do not indicate as great a con- 

 striction as in skulls of males. 

 Frontals broad; temporal ridges 

 quite prominent and placed quite 

 close together before reaching the 

 inion, but not forming a sagittal 

 crest. Brain-case broad, zygo- 

 matic arches light. Skull rather 

 broad and low, to a great extent 

 brought about by crushing. 



Skull slightly depressed by crush- 

 ing. 



Nasal horn-cores very robust, 

 nasals extend in front of premaxil- 

 laries, bluntly pointed anteriorly 

 and gently constricted back of horn- 

 cores; frontals broad; temporal 

 ridges prominent and remaining far 

 apart all the way back to the occi- 

 put. Brain-case large; zygomatic 

 arches very robust on the posterior 

 angle. Skull rather low and broad. 



Small functionless and persistent 

 canines indicated on both sides. 

 P' much worn. P- with no crista, 

 but a weak crochet, the latter being 

 double on tooth of left side; a small 

 antecrochet present on this tooth of 

 the right and left jaws and the 

 post-fossette nearly enclosed. P' 

 without crista, crochet also poorly 

 developed, crenulated, and post-fos- 

 settes isolated by wear. P* with 

 weak crista and crochet. All the 

 premolars with strong cingulum in- 

 ternally. M' with no crista, but 

 heavy crochet, a minute tubercle in 

 the median valley; a large post- 

 fossette and no cingulum on internal 

 face of the tooth. M- with weak 

 crista but strong crochet, a very 

 minute tubercle in the median 

 valley, post-fossette broadly open 

 and cingulum only faintly indicated 

 on the internal faces of the tooth. 

 M' has received little or no wear. 

 Crista and crochet very poorly de- 

 veloped. 



P' much worn. P'^ with medi- 

 and prefossettes quite distinct; 

 crochet with crenulated border, 

 post-fossette large. P' quite worn, 

 but medifossette indicated. Crochet 

 nearly united with ectoloph. Post- 

 fossettes quite large. P^ with medi- 

 fossette (especially on the tooth of 

 right side) isolated, prefossette and 

 median valley united. Post-fossette 

 large. Premolars with heavy cin- 

 gulum. ]VP much worn, no crista, 

 crochet nearly united with ectoloph; 

 post-fossette large, cingulum weak. 

 M- with strong crista and crochet 

 (the two nearly meeting on tooth of 

 right side). Post-fossette large. M' 

 with crista and crochet much better 

 developed on tooth of left side, 

 cingulum weak on molars. 



Dentition represented only by P' 

 and P^ and M' and M^ P' with no 

 crista; crochet strong, crenulated 

 internally and nearl)' united with 

 ectoloph. Post-fossette large. P* 

 with no crista, crochet strong an 

 crenulated, as on tooth in advance 

 of it. Post-fossette large. M' with 

 no crista, but strong crochet, which 

 on a little further wear would unite 

 with the ectoloph. Post-fossette 

 nearly isolated by wear. M- with 

 prominent crista and crochet. A 

 tendency to develop a small tubercle 

 in the median valley. Post-fossette 

 large. The premolars have cingulum 

 better developed than on the molars. 



