410 ORDERS OF MAMMALIA. 



Myarioii, supposed to be nearly allied to the existing Hcs- 

 peromys of North America. 



The genus Cricetus, comprising the existing Hamster, is 

 known to occur in the Pliocene deposits of Europe, and is 

 represented in Post-Tertiary deposits by a form probably 

 identical with the living C. xulgaris. The Lemmings 

 {Myocles) are represented by at least one species in Post- 

 Tertiary deposits in Britain, occurring after the Glacial 

 period, and being contemporary with " palaeolithic " man. 

 The Voles or Campagnols (Arvicolo,) commence in the 

 Pliocene, and are abundantly represented in Post-Tertiary 

 deposits. The Post-Glacial deposits of Britain have yielded 

 remains of the Arvicola 23'^'ci'i^nsis, A. agrestis, and A. am- 

 ■pJiihia, the last of which (the well-known " Water-rat ") 

 occurs also in Pree-Glacial accumulations. 



Fam. 10. Dipodidce. — The next family of the Rodents, 

 which is sufficiently important to need notice, is that of the 

 Dipodidce or Jerboas, mainly characterised by the dispropor- 

 tionate length of the hind-limbs as compared with the fore- 

 limbs. The tail also is long and hairy, and there are com- 

 plete clavicles. 



The genus Dipus itself is stated to occur in the Miocene 

 Tertiary of Europe ; and the French Pliocene has yielded 

 remains of the extinct genus Issiodroniys, supposed to be allied 

 to the existing Jumping Hares (Fcdetes) of Southern Africa. 



Fam. 11. Myoxidm. — The members of tliis family are 

 commonly known as Dormice, and they are often included 

 in the following family of the Squirrels and Marmots. 



They resemble the Squirrels in most respects, but they 

 have only four molars on each side of the upper jaw, whereas 

 the latter possess five. Two species of Myoxus have been 

 detected in the Upper Eocene (Gypseous series of Mont- 

 martre), and a third species has been determined from beds 

 of Miocene age. Several species have been detected in 

 Post-Tertiary deposits, of which the most remarkable is the 

 comparatively gigantic Myoxus Mditensis of the Maltese Post- 

 Pliocene. This form is described by Ealconer as being " as 

 big in comparison to the living Dormouse as the Bandicoot- 

 rat to a Mouse." 



