Cope.] 384 [Oct. 7, 



The ancestral geuus is bunodont, without diastemata, and with well- 

 developed canines. The hypothetical genus (1) is selenodont, with short 

 diastema, and well-developed canines. 



The certainly known genera of the XiPHODONTiDiE are four, which 

 differ as follows : 



Molars bunodont ; diastemata ; canines large Rhagatlierium Pict, 



Molars selenodont ; diastemata ; canines nxG^ixxm.. Xiphodontotlierium Filh. 

 Molars selenodont ; no diastemata ; canines not distinct in form 



Xiphodon Cuv. 



Molars selenodont ; no diastemata ; superior canine developed; inferior 



p. m. 1 functioning as canine Protoreodon S. & O. 



Cryptomeryx Schl. prbbably belongs here. 



The relations of these genera are clearly somewhat like those of the 

 preceding family. The bunodont condition of the molars of Rhagathe- 

 rium is primitive, while its diastemata are the reverse. The continuous 

 dental series of Xiphodon is primitive, while the detailed structure of the 

 molars is advanced. These relations may be thus shown : • 



Xiphodontotherium 

 Protoreodon y 



Xiphodon 



Rhagatherium 



The hypothetical genus 1 is simply a bunodont without diastemata, and 

 with well-developed canines. 



The pigs, SuiD^, are an old family, although no genus is known prior 

 to Miocene time. The genera present considerable variety among them- 

 selves, but some of the existing genera differ very little from some of the 

 earliest. The greatest diversity is seen in the modifications of the incisor 

 and canine teeth. ■ The following represents the characters : 



I. Metapodials fused proximally (Dicotylinte). 



a. Premolars like molars. 



Premolars | ; cusps of molars separate Dicotyles Cuv. 



Premolars f ; cusps of molars united into partial cross-crests 



Platygonus Lee. 



II. Metapodials distinct (in some unknown) ; molars without cement- 



um ; incisors normal (Suinse). 



a. Fourth premolar with one external tubercle. 



Four superior premolars Thinohyus Marsh. 



Three superior premolars ... Ohmnohyus Cope. 



aa. Fourth superior premolar with two external tubercles. 



