26 



MAMMALIA 



These are possibly the descendants of Plagiaulacidae. Their relationship 

 with the Caenolestidae is rather doubtful on account of their large size, although 

 there are certain resemblances between Polydolops and Ahderites. 



The family is represented by numerous genera established by Ameghino 

 mostly upon detached teeth. Orthodolops and Aviphidolops have the tubercles 





Fig. 37. 



Polydolops thomasi Ameghino. Notostylops strata of Eocene ; Patagonia. A, Upper tootli row. 

 B, External aspect of lower tooth row. C, B from above. D, PHodulops primutus Ameghino. Same 

 locality. Upper M. */i. (After Ameghino.) 



but slightly differentiated, and Polydolops (Fig. 37, A-C), Pseudolops and Pliodolops 



have them well defined. Pliodolops (Fig. 37, D) has the tubercles of the upper 



molars arranged in several series. 



1.0.2.3. 

 Propolymastodon {Promysops 1) Ameghino (Fig. 38) is distinguished 



from the other genera in possessing only one very simple, non-corrugated lower P. 



Eommanodon Ameghino. 

 Miocene (Colpodon beds). 

 Sj^stematic position doubt- 

 * ^ ful. 



^ Suborder B. 



C^k^^:^ DIPROTODONTIA Owen. 



Clbiefly herbivorous forms 

 with four quadrihihermlar or 

 two ridged M. P similar to 

 M 07- laterally compressed 

 {lamellar ?) and trenchant. C lacking or very minute. Above, 4-1 /, of which the 

 foremost is enlarged ; below, only a single, very strong, rodent-like I. 



The Diprotodontia are possibly descendants of Polyprotodontia, which have 

 adapted themselves to a mixed or exclusively herbivorous diet. With the 

 exception of the South American genus Caenolestes they are confined to Australia, 

 wliere they also exist in the Pleistocene. From the Tertiary of Patagonia a 

 number of extinct genera and species are known. 



Fio. 38. 

 A, Propolymastodon caroli ameghinoi Ameghino. Lower jaw, 2/j. 

 B, P. acuminatus Ameghino. Left last lower M, 2/j. C, P. cardatus 

 Ameghino. Lower tooth row with exception of last M., seen from 

 above, i/j. Notostylops strata of Upper Eocene ; Patagonia. 



