AMEGHIXO: LES FOEMATIONS SÉDIMENTAIEES. 



241 



a conclusión would be quite erroneons. The genera are all extinct 

 and a considerable number of them have left no successors: these 

 latter are, fort the most part, the more or less modified snrvivors 

 of earlier faunas and, for that reason, are often of great phyloge- 

 netic importance. » 



« The subjoined table, wieh follows Thomas, arrangement of 

 families and subfamilies, will serve to give an idea of the eompa- 

 rative number of the hystricomorph rodents of South America in 

 Santa Cruz and in recent times. » 



Ctenomys 



Aconaemys 



Spalacopus 



Octodon 



Abrocoma 



Dactj'lomys 



Thrinacodus 



Kannabateomys 



Loncheres 



Thricomj-s 



Cercomys 



Carterodon 



Mesomj's 



Echimys 



Myocastor 

 Capromys 

 Plagiodontia 



Coendú 



Chaetomj-s 



AVantiní 



Viscaccia 



Chinchilla 



Lagidium 



I. OCTODOXTIDAE. 

 1. Ododontinae. 



2. Loncherinae. 



3. Capromynae. 



11. EEETHIZONTIDAE. 



1. Erethizontinae. 



2. Choetomyinae. 

 3. Acaremyinae. 



II [. CHINCHILLIDAE. 



SAXTA CRUZ 



Not found 



Anal. Mus. Nac. Bs. As., Sek. 3*, t. viii. Junio 14, 1906. 



Stichomj^s 



Adelphoniys 



Gyrignophus 



Spaniomys 



Graphimys 



Xeoromys 

 Scleromys 

 Lomomy.s 

 Olenopsis 



Steiromvá 



Xot found 



Acaremj's 

 Sciamj's 



Prolagostomus 



Pliolagostomus 

 Scotaeumys 

 Perimys 

 Sphodromys 



16 



