141 8 CLASS MAMMALIA. 



have simple cusps, and are rooted. Paciculus, from the Miocene of 

 the United States, is allied to the next genus, but has enamel-folds 

 to the molars. Neotoma is represented by a species in the Pleisto- 

 cene of the Pennsylvanian caves, which is perhaps not distinct from 

 the living Florida-Rat. The genus Cricetus, typically represented 

 by the European Hamsters, is taken by Mr O. Thomas to include 

 the American Hesfieromys. It is represented sparingly in the Pleis- 

 tocene of Europe ; but it is probable that Cricetodon (Decticus), 

 which ranges from the Quercy Phosphorites to the Middle Miocene 

 of France, cannot be generically separated. In America fossil forms 

 occur abundantly in the Brazilian cave-deposits, where they have 

 been described as Hesperomys ; and it is probable that we must 

 include in the same large genus (Cricetus) the so-called Eumys of 

 the Miocene of North America. The subfamily Deomyincz is only 

 known by Deomys, of the Congo Valley, which has upper molars 

 intermediate in structure between those of the preceding and follow- 

 ing subfamilies. The Murine, or more specialised Mice, are mainly 

 characteristic of the Old World, and do not date back far in time. 

 Their upper molars have the cusps or tubercles arranged in three 

 longitudinal rows and well-developed roots. Mus, or the closely 

 allied Acomys, is first known from the Pliocene Pikermi beds, and 

 thence is found through the Pleistocene of Europe. The Australian 

 genera Hapalotis and Mastacomys are represented by existing species 

 in the cave-deposits of that country. The Indian Phlceomyince, hav- 

 ing broad upper incisors, and rooted molars 

 with transverse laminae, are represented in 

 the Pleistocene of Madras by two species of 

 Nesocia identical with those now inhabiting 

 the same area. The Gerbillince also have 

 laminated molars (fig. 1295), but the upper 

 incisors are narrow and the hind limbs 

 elongated. The existing Gerbillus indicus 

 ofS m \ 2 n 9 d 5 iweTtd e the r wr occurs fossil in the Madras caves. The 

 molars (enlarged) of Gerbiiius i as t molar' in both the upper and lower 



indicus; from a cave in Ma- . . 



dras. jaws of this genus has only a single trans- 



verse lamina, as shown in the figure. 

 Lastly the Sminthince, in which there is a premolar in the upper 

 jaw, are represented by the existing Sminthus vagans in the Pleisto- 

 cene of Europe. 



Family Myoxid^e. — In the Dormice the number of the cheek- 

 1 3 



teeth is Pm. -, M. - ; these being rooted, with complex enamel- 

 folds. For palseontological purposes all the forms may be included 

 in Myoxus, which commences in the Paris gypsum and Quercy 

 Phosphorites, and is represented in the Pleistocene of Malta by a 



