400 ORDERS OF MAMMALIA. 



In the true Dogs, on the other hand, an upper molar is 

 missing, and there are thus only two tubercular teeth behind 

 the upper carnassial (the fourth premolar) ; the dental 

 formula being — 



.3—3 1—1 4—4 2—2 ,^ 

 ^ : c - - ; J9^«' ; m = 42. 



3—3 1—1 4—4 3—3 



In the Pliocene period, especially in North America, 

 species of Canis seem to have abounded, and the same is true 

 of the Post-Pliocene, some of the Post-Tertiary forms being 

 nearly or quite inseparable from existing species. Thus, 

 the so-called Canis familiaris fossilis of the caves of Germany, 

 Belgium, and Prance, appears to be very nearly allied to the 

 domestic Dog of the present day. Similarly, the so-called 

 Canis spdmus, and Canis vulpcs spcla'us are nearly, if not 

 quite, identical with the existing Wolf and Fox of Europe. 



We may here intercalate the singular extinct genus 

 Hi/amodon, with its allies, for which it is necessary to estab- 

 lish the distinct family of the Hj/amodontida;. Hycanodon is 

 found in the Eocene and Miocene Tertiary of Europe, and in 

 deposits of the latter age in North America, and is remark- 

 able on account of the nature of its teeth. The dentition 

 is complete, the dental formula being — 



. 3—3 1—1 4—4 3—3 , , 



% ; c ; pm ; m = 44. 



3 — 3 1 — 1 4 — 4 3 — 3 



Moreover, there is the character — unexampled among the 

 existing Carnivores — that all the molars have trenchant 

 edges, and are of the " carnassial " or sectorial form ; and 

 there are no "tubercular" molars (fig. 679). In this respect 

 Hya^nodon approximates to the living Marsupial genus Tliyla- 

 cinus. The extinct genus Pterodon of the European Eocene 

 is nearly allied to Hywiiodon, as is also the Dromocyon of the 

 Middle Eocene of North America. The latter, however, has 

 only four lower incisors. Mcsonyx and Limnocyon, of the 

 American Eocene, also seem to properly find a place in the 

 family of the Hyoiiiodontida?, though the former has some 

 very peculiar characters. 



The last group of the Digitigrada is that of the Felida:, or 



