little curved, and the outer elevated crest, uninterrupted. A short 

 elevated fold proceeds from the latter, dividing the head of the trans- 

 verse valley. A compressed conic tubercle stands between the inner ex- 

 tremities of the crests. The first premolar has two transverse crests 

 and an anterior tubercle. The posterior creet is strongly curved back- 

 wards at its inner end. A strong cingulum surrounds the base of the 

 crown except on the outer side. 



Measurements. 



M. ' 



Length of three anterior molars 090 



" third molar 030 



Width " " 033 



Length of first " 026 



Width " " 019 



This species is twice as large as the largest known species of the 

 genus. 



Hyracodon arcidens, sp. nov. 

 Established on the premaxillary and molar dentition, as far as the fifth 

 tooth of the left upper jaw. The species is intermediate in size between 

 the two last, but is nearer in this and other respects to the H. tapiranus. 

 The molars have the outer longitudinal aud inner transverse crests, the 

 posterior short, the anterior much curved backwards round it, and thus 

 forming the inner boundary of the tooth wall. The first premolar is 

 shorter than the others and has a short anterior lobe . The milk molars 

 show more nearly transverse crests as in RMnocerus, but the first pre- 

 molar had the anterior lobe. Canine and first incisor short, conic ; 

 second incisor with an outer lobe ; median incisor transverse. Enamel 

 smooth. 



M. 



Length of four superior molars 0.072 



" diastema 006 



" canine and incisors 020 



" first premolar 014 



Width " " 012 



Length of third " 021 



Width " " 022 



Height " " 025 



Portions of two or three individuals found. 



Symborodon torrus. Gen. et sp. nov. 

 The horned mammals of the present period are, as is well known, the 

 Artiodactyla. In the discovery of the genera Loxolophodon, Eobasileus, 

 etc., I was afforded opportunity of showing that the horned types of the 

 Eocene were Proboscidians of an aberrant type. The present notice in- . 

 troduces a series of forms from the Miocene with a familiar armature of 

 osseous horns, which are all true Perissodactyles, and allied to the 



