638 LAND MAMMALS IN THE WESTEKN HEMISPHERE 



torn out, the circular puncture of the enemy's bite being un- 

 mistakable and the healed edges of the wound proving that 

 the loss of the tooth was suffered during life. In structure, 

 these smaller animals differed so little from the larger ones, 

 that no particular description of them is needed. In the 

 restoration of \Cladosictis (Fig. 300) the spotted pattern of 

 the Australian dasyures, or native cats, has been taken as a 

 model. 



In the Deseado formation the predaceous marsupials have 

 been less abundantly found than in the Santa Cruz and there 

 can be little doubt that the group is very inadequately repre- 

 sented by the material so far collected. Only two genera, 

 known from lower jaws, have been described, but one of these 

 {fProborhycena) is of interest because of its enormous size, 

 far surpassing any of the Santa Cruz forms and equalling the 

 largest modern bears. This is another illustration of the un- 

 usual relationship between the Deseado and Santa Cruz 

 faunas, the older stage so frequently having the larger 

 animals. 



Predaceous marsupials of small size may be traced back to 

 the Casa Mayor formation, but very Uttle is yet known of 

 them. There is no obvious difficulty in the way of their 

 derivation from opossum-like . forms, such as are foimd in the 

 Cretaceous of North America and probably of South America 

 also. 



The relation of the South American to the AustraUan 

 marsupials offers problems of unusual interest, a discussion 

 of which would be impracticable here. Several alternative 

 solutions of the problem have been offered and great differences 

 of opinion exist with regard to it. To my mind the most 

 probable suggestion is that a land-connection, by way of the 

 Antarctic continent, existed in early Tertiary times, by means 

 of which the ancestors of the Australian marsupials migrated 

 from South America, though this explanation is rejected by 

 several eminent authorities. 



