45 8 ORDERS OF MAMMALIA. 



with five toes, and are considerably shorter than the hind-legs, 

 which have only four toes. The two orbits communicate by 

 an aperture in the septum. Generally there is a short erect tail. 



Species of Lepus, more or less nearly allied to the existing 

 Hares and Rabbits, are found in the Miocene and Pliocene 

 Tertiary of Europe ; whilst the Post-Tertiary deposits of the 

 same area have yielded remains almost or quite identical with 

 living species. The cave-deposits of Brazil have also yielded 

 the bones of a hare very nearly allied to the living Lepus 

 Brasiliensis. The Calling Hares or Pikas (Lagomys), which 

 are distinguished by their nearly complete clavicles and rudi- 

 mentary tail, and which at the present day are characteristic of 

 Siberia, are found in the Pliocene of Oeningen and in Post- 

 Tertiary deposits in Britain and Southern Europe. 



Fam. 2. Cavidce. In this family are the living Capybaras 

 (Hydrochcsrus\ Agoutis (Dasyprocta), Pacas (Ccelogenys), &c, 

 characterised by their absence of clavicles, their rudimentary 

 tail, their unguiculate toes, and their general possession of 

 eight rootless molars in each jaw. Almost all the existing 

 members of this family belong to South America, and this 

 continent has been peopled during Post-Tertiary times with 

 numerous species more or less nearly allied to living forms. 

 Thus, the Brazilian bone-caves have yielded to the researches 

 of Lund remains of Guinea-pigs (Ancema), Agoutis, Pacas, and 

 Capybaras, all of which appear to belong to extinct species. 



Fam. 3. Hystricida. In this family are the well-known Por- 

 cupines, distinguished from the other Rodents by the fact that 

 the body is covered with long spines or " quills," mixed with 

 bristly hairs. They have four molars on each side of each jaw, 

 and they possess imperfect clavicles. 



Remains of Porcupines allied to the existing species of 

 Hystrix have been detected in the Pliocene and Post-Pliocene 

 deposits of Europe and Asia. On the other hand, the bone- 

 caves of Brazil have yielded the remains of a Porcupine with 

 a prehensile tail, allied to the living Cercolabes of South 

 America. 



Fam. 4. Castoridce. The best-known example of this family 

 is the Beaver (Castor fiber). The distinctive peculiarities of 

 the family are the possession of distinct clavicles, the posses- 

 sion of five toes to each foot, and the fact that the hinder feet 

 are mostly webbed, adapting the animal to a semi-aquatic life. 



The genus Castor, comprising the existing Beaver, and 

 characterised by the possession of a flattened scaly tail, is re- 

 presented by fossil species in the Miocene and Pliocene de- 

 posits of Europe. The Castor spelaus of the European cave- 



