SUBORDER A 



SIMPLICIDENTATA 



109 



Subfamily 2. Theridomyinae. 



Cheek teeth lophodont. Cusps recognisable only in the oldest forms, being worn 

 down in later forms, with three to four outer folds and one inner fold on the 

 upper teeth, and three to four inner and one or two outer folds on the lower teeth. 

 D usually more complicated than P. Tibia and fibula free. In the Eocene, 

 Oligocene and Miocene of Europe. 



This subfamily has a common origin with the foregoing, and is the ancestor 

 of certain Hystricoidea — Capromyinae, Erethizontinae, Ocfodontinae, Chinchillinae 



and Echinomyinae. 



Theridomys Jourdan (Fig. 136). 

 P always larger than M. Eocene ; 

 D6bruge, Vaucluse. Swabian 

 and Swiss Bohnerz. Oligocene 

 Phosphorites, and Eonzon, 



Fig. 136. 



A and B, Upper and lower tooth-row of Theridomys vaillanti 

 Gervais. '■^/j. Upper Eocene of Debruge (Vaucluse). C, D, E 

 and F, Theridomys gregarius Schlosser. Oligocene (Phos- 

 phorite) of Quercy. C, Ijower jaw ; D, upper tooth-row with 

 I>4 ; E, lower D^ ; F, lower tooth-row with P^. 3/j. 



Fig. 137. 



Protechimys major Schlosser. Oligocene 

 (Phosphorite) of Quercy. a, Upper and h, 

 lower tooth-row. 3/i. 



Trechomys Lartet. P usually much smaller than M. D simple. Eocene ; 

 Paris. Phosphorites of Quercy. 



Phiomys Osborn. Middle transverse ridge short. Oligocene ; Egypt. 



Protechimys Schlosser (Fig. 137). Folds oblique. Cheek teeth cleft 

 on account of the fusion of the outer and inner folds. Crowns somewhat 

 hypsodont. Phosphorites of Quercy. 



Archaeomys Laiz. et Parieu. Similar to the last. Crowns of the teeth 

 rather hypsodont. Oligocene ; Dept. Allier, France. 



Pihodanomys Dep6ret. Lower Miocene of Savoy and Ulm. 



1^ 

 1-0 



Family 6. Myoxoidea. Dormice. 

 P. |- M. Cheek teeth always brachyodont with 



parallel or converging enamel ridges. Infraorbital canal large 

 and in an elevated position. Tibia and fibula fused. Recent 

 in the Palaearctic and Ethiopian regions. 



Of the species having four cheek teeth, almost all 

 were represented in the European Tertiary. 



Myoxus Schreber (Fig. 138 J). Probably already in 

 the Eocene (Phosphorites, Paris gypsum 1), but definitely 

 known from the Miocene. 



A, Myoxus sansanicnsis 

 Lartet. Upper Miocene of 

 Ries. Upper molars. 6/1. 



B, Eliom.ys hamadryas F. 

 Major. Upper Miocene of 

 Steinheira. Lower molars. 



