402 ORDERS OF MAMMALIA. 



1—1 3—3 1—1 



c ; ])m ; m = 30. 



3—3 1—1 " 2—2 1—1 



The legs are nearly of equal size, and the hind-feet have 

 only four toes each, whilst the fore-feet have five. All the 

 toes are furnished with strong, curved, retractile claws, which, 

 when not in use, are withdrawn within sheaths by the action 

 of elastic ligaments, so as not to be unnecessarily blunted. 



The earliest known type of the true Fclidce would seem 

 to be the Limnofelis of the Middle Eocene of North America, 

 which appears to be a genuine Cat, though its structure is 

 not fully known. There are also other Eocene types, which, 

 when fully understood, may prove to be referable to this 

 family. In the Miocene period true Fdidm abounded, as 

 also in the Pliocene, both in Europe and North America. 

 In addition to various forms referable to the existing genus 

 Felis, the Miocene deposits have yielded the remains of the 

 singular extinct genera Psciidmlurus, Diiiictis, and MacJiair- 

 odus. The first of these differs from Felis proper, in pos- 

 sessing an additional pra^molar in the lower jaw, and it is 

 found in the Miocene of Europe and the Pliocene of North 

 America. Dinictis, on the other hand, not only has an ad- 

 ditional lower prajmolar on each side, but it possesses a 

 minute tubercular molar behind the carnassial tooth. It 

 occurs in the Miocene of North America. Lastly, the genus 

 Machairodus includes the so-called " sabre-toothed Tigers," 

 and is widely distributed both in space and time, ranging 

 from the Miocene to the close of the Post-Pliocene, and 

 being already known to occur in Britain, in the Continent 

 of Europe, in India, and in North and South America. 

 Machairodus presents us with the Carnivorous type in the 

 most specialised condition at present known ; the upper 

 canines being extraordinarily developed, trenchant, and 

 sabre-shaped, with finely-serrated margins (fig. 681). No 

 true molar is present in the upper jaw, and the prtemolars 

 are reduced to two on each side of each jaw. The dental 

 formula is — 



.3—3 1 — 1 2—2 0-0 ^^ 



^ ; c : pm ; m - — = 20. 



3 — 3 1—1 ' ^ 2 — 2 1 — 1 



