118 THE AGE OF MAMMALS 



includes a continuation of the old mammals of the Upper Thanetian (Cer- 

 naysian), and partly a number of mammals now recorded or observed for 

 the first time. Among the former is the insectivore Adapisoriculus, pos- 

 sibly related to Adapisorex of the Cernaysian, Plesiadapis, which resembles 

 Mixodedes of the American Torrejon in its diprotodont dentition. The 

 skull and skeletal characters do not agree well with those of modern insec- 

 tivores, nor are they distinctively primate (Matthew). Protoadapis also 

 appears, and like Plesiadapis is of doubtful primate reference; it has been 

 classed with the Rodentia, or may be placed with Mixodedes among the 

 Proglires. Creodonts are represented by Hycenodidis, allied to the mesony- 

 chids in tooth structure; the rodents by Dedicadapis and Plesiardomys. 

 The odd-toed Ungulata are represented by two out of four great branches 

 or phyla of the Lophiodontidse which are destined to play a great part in 

 the Eocene mammal life, namely, by the more robust form Lophiodon 

 remense (of about the size of a tapir and ancestral to the great L. lauiricense 

 of the Upper Eocene) and by Chasmotherium, a small lophiodont lacking 

 the third lobe of the last lower molar (ancestral to the C. cartieri of the 

 Upper Eocene). These chasmotheres are of small size, the premolar teeth 

 rapidly complicating; they tend to be short-headed, or brachycephalic, 

 the teeth finally forming a closed series. The other phylum parallels the 

 more robust lophiodons and survives until the close of the Middle Eocene. 

 Deperet considers the ' Propachynolophus ' gaudryi (Lemoine) of these beds 

 as a member of the Equidse, but in the present writer's opinion the ad- 

 vanced condition of its grinding teeth, its considerable size, the presence 

 of a mesostyle in the grinding teeth above and of a metastylid below ap- 

 pear to liken it rather to a primitive palseothere {IPlagiolophus). The 

 smaller Propachynolophus maldani (the type of this species and genus), 

 however, may be truly a hyracothere, or primitive horse. The Artio- 

 dactyla are now for the first time represented by the small pro-ruminant 

 form Protodichobune. 



Altogether the affinities of these animals await solution by much further 

 study and comparison. 



In deposits alleged to be of Upper Ypresian age in southeastern Europe 

 (Transylvania) are found the remains of a large quadruped (Brachydias- 

 tematherium) related to the American family of titanotheres (see p. 556). 

 This animal is in an Upper Eocene stage of evolution comparable to that 

 of the American Protitanotheriu?n (p. 169). It thus appears probable that 

 these deposits are much more recent than Lower Eocene. 



Lower Eocene, Wasatch and Wind River Life of North America 



The Lower Eocene of North America is the great Coryphodon Zone ; 

 it is represented by a grand fauna known from thirty-eight years of 

 exploration in formations which are broadly known as "Wasatch," this 



