110 RODENTIA oeder vi 



Eliomys Wagner (Fig. 138 B). Miocene. Muscardinus Wagner. Fossil 

 in the Pleistocene. 



Leithia Lydekker. Pleistocene of Malta. 



Family 7. Dipodoidea. Jumping Mice. 



T) -5" ^^ -o" -^^ I" ^- Cheek teeth brachyodont, usually rooted, with alternating 

 cusps. Infraorlital canal large and round. Fibula and tibia fiised. Hind-limb 

 elongated, metatarsals often fused. 



The jumping mice inhabit at present the deserts and steppes of the 

 northern hemisphere. The fossil remains belong to living genei'a and species, 

 and are only known from the European Pleistocene. 



The Zapodinae have five free metatarsals. Sminthus Keys. Also fossil 

 in Europe. 



The three middle metatarsals of the Dipodinae are very much elongated 

 and fused throughout their complete length. 



Alactaga Cuvier. Pes three-toed. Pleistocene of Europe. 



Dipus Gmelin. Pes five-toed. 



Sciuromys Schlosser. \ P- % M- Teeth similar to those of Alactaga. 

 Phosphorites of Quercy. Systematic position uncertain. 



Family 8. Myoidea (Myomorpha). 



3-2 



(? ^ P) ^~ M. Infraorbital foramen large. Zygomatic arch small. Cheek teeth 



brachyodont, btmodont or lophodont or else hypsodont, prismatic. First M, as a rule, 

 large and more complicated than M^ and M^. Lower jaw with high coronoid process. 

 Angle of the loiver jaw arising from the inferior surface of the incisor alveolus. 

 Fibula fused with the tibia. 



The Myoidea are usually small, and are at present dispersed over the 

 entire earth's surface. 



Subfamily 1. Eomyinae. 



i P. I" M. Cheek teeth brachyodont, with two opposing pairs of cusps, and 

 considerable front and hind surface and ridge running along the centre of the tooth. 

 Oligocene of Europe and North America. 



These small rodents are placed by Winge under the Dipodoidea and by 

 Scott under the Geomyidae. The dental arrangement, as in Cricetodon, makes 

 it possible for these forms to be considered as primitive Murinae. 



Eomys Schlosser. Phosphorites of Quercy. 



Gymrwptychus Leidy. Skull as in Geomyinae, but teeth brachyodont. 

 Oligocene (White River beds). 



Subfamily 2. Cricetinae. Hamsters. 



f M. Cheek teeth bunodont, roofed, with four paired regularly arranged cusps. 

 M^ with five or six tubercles. 



The Cricetinae inhabit the northern hemisphere. 



