SUBORDER A 



SIMPLICIDENTATA 



113 



Coendu Lac6p. Eecent in South America. Fossil in the bone caverns of 

 Brazil. 



Erethizon F. Cuvier. Recent and in the Pleistocene of North America. 



Sciamys and Acaremys Amegh. (Fig. 143) in the Miocene of Santa Cruz and 

 Frotacaremys Amegh. in the Colpodon 

 beds of Patagonia, are small forms. 



^r^: 



"-^r 



Subfamily 3. Capromyinae. 



Teeth shaped like those of Castoridae. 

 Usually moderate-sized forms. Descend- 

 ants of Theridomys 1 



Myocastor Kerr (Myopotamus Geofir.). 

 Recent in South America. Fossil in 

 the Pliocene. 



Morenia, Discolomys Ameghino. 

 Pliocene of Argentina. 



Neoreomys Ameghino, in the Santa Cruz formation of Patagonia 

 genera Sderomys and Lomomys Ameghino are from the same locality. 



Fig. 143. 



Acaremys messor Amegh. Upper Miocene of Santa 

 Cruz, Patagonia, a. Mandible, i/i i i>, upper tooth- 

 row without M^ ; c, lower tooth-row ; d, lower D4, 



•■Vi- 



The 



Subfamily 4. Octodontinae. 



The group of Octodontinae arises in the Pliocene of Argentina with 

 Dicoelophorus and Plataeomys of Ameghino. Ctenomys Blv. first appears in the 

 Pleistocene of South America. The group of Loncherinae has representatives 

 in the early Miocene of Patagonia (Colpodon beds), such as Frotadelphomys 

 and Prospaniomys. In the Miocene of Santa Cruz are found Stichomys, Adel- 



phomys, Spaniomys (Fig. 144), etc., 

 M?>An-^-/¥mn-\ ^^ Ameghino. Loncheres Illiger, 



uM!^i\lll^]v»>jilS' Echinomys and Mesomys Desm. are 



rtM^^W^ known from fossil remains in 

 Brazilian caves. 



^^jf' 



Subfamily 5. Chinchillinae. 



Fig. 144. 



Spaniomys modestus Amegh. 

 a, Upper tooth-row; 6, lower 

 tooth-row with exception of M. 

 3/1. Upper Miocene of Santa 

 Cruz, Patagonia. 



Fio. 145. 



Perimys ereotus 

 Amegh. Upper Mio- 

 cene of Santa Cruz. 

 a, Upper, and 6, lower 

 tooth-row. i/j. 



Usually only one enamel fold ex- 

 tending transversely across the grind- 

 ing surface. This family probably 

 originates in the European genus 

 Archaeomys. 



Prolagostomus, Pliolagosfomus 

 Ameghino. Santa Cruz beds. Ancestors of Lagostomus Brooks, fossil in the 

 Pliocene and onwards. Also Recent. 



Perimys Ameghino (Fig. 145). Colpodon beds and Santa Cruz formation 

 of Patagonia. 



Scotaeumys, Sphodromys Ameghino. 



Megamys Laurillard. The largest fossil rodent. Pliocene and Pleistocene 

 of Argentina. 



VOL. Ill 



