xin PHYLUM CHORDATA 589 



The ulna and fibula are complete, and there are either four or five 

 fully formed digits in each foot. The Toxodontia approach 

 nearer the normal Ungulate type, the clavicle and the foramen over 

 the inner condyle being both absent. They have a massive skull 

 and short stout limbs, each with three digits. 



The true Carnivora of the Tertiary period are, as compared with 

 those of the present time, remarkable for the absence of the well- 

 marked distinction into groups such as are now to be recognised ; 

 numerous intermediate forms connect together the Dogs, Civets, 

 Cats, Bears, and Weasels, which, in the existing fauna, appear 

 separated from one another by differences of the most strongly 

 marked character. Several extinct families are recognised, and 

 one extinct order the Creodonta. The latter present resemblances 

 to the Insectivora on the one hand, and to the Polyp rotodont 



FIG. 1248. Tillotherium fodiens. Left lateral view of skull. (From Flower, after 



Marsh.) 



Marsupials on the other, such as would appear to indicate a 

 relationship with both of those groups. 



A group of Eocene Mammals of uncertain affinities are the 

 Tillodontia (Fig. 1248), which by some have been elevated to the 

 rank of a distinct order. The Tillodontia appear to unite in a 

 remarkable degree, in skull and dentition, ungulate, rodent, and 

 carnivorous characteristics. 



The Rodents were represented in the Tertiary period by all, or 

 nearly all, the principal groups existing at the present day, together 

 with several extinct families. Some of the Tertiary Rodents 

 attained a much larger size than any living members of the order. 



Among the Tertiary Insectivora, in addition to representatives 

 of existing families, are a number of extinct forms. Through these 

 it is possible to connect the living Insectivora with the Creodont 

 Carnivora on the one hand, and with the Prosimii on the other. 



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