ORIGIN AND DISTRIBUTION OF MAMMALS 293 



earlier Mesonychidae, Ardocyonidae and Miacidae, and their Lower Eocene 

 representatives, is not so great that a genetic connection between these faunas 

 must be absolutely denied. 



Though the fauna of the Lower Eocene in North America has yielded a large 

 number of species, genera and families, it is only during the Middle Eocene 

 that a varied animal distribution appears in Europe. The most important 

 localities in Europe are Argenton (Indre), the Parisian Calcaire Grossier, 

 La Liviniere, Cesseras and Issel in southern France, Bracklesham in England, 

 Buchsweiler in Alsace and the Bohnerz of Lissieu, Chamblon and Egerkingen. 

 The fauna of the Bohnerz was widely considered up to a short time ago to be 

 merely a mixture of mammalian teeth from many different strata of the 

 Tertiary, since the greatest variety of animal remains seemed to have been found 

 in the same locality. This was so, largely because experts only supervised 

 the excavations in exceptional cases, and because the remains were segregated 

 according to the state of preservation and the place of their origin in the 

 different strata. Closer observation, however, made possible a very exact 

 division between the different faunas of the south German and the Swiss 

 Bohnerz. Therefore we can well state that only contemporaneous remains 

 were interned in a single stratum. 



In the fauna of the European Middle Eocene the perissodactyls are without 

 a doubt the most important fossils. Those resembling the tapir are represented 

 by Chasmotherinm and Lophiodon, those most like horses, by Falaeotheriuiii, 

 Propalaeotherium, Paloplotherium, Lnphiotherium., Anchilophus and Pachynolophus. 

 The artiodactyls, on the contrary, are very sparsely represented in the earlier 

 part of this period, in the lower Lutetian only by the Dichohunidae, — Dichohme, 

 Meniscodon, and Anoplotheriidae, — by Catodontherium, Dacrytherium and by the 

 somewhat puzzling genus Tapindus. Only in the Upper Lutetian are found 

 the Suidae — Cehochoerus and Choeromorus, — the Anthracotheriidae — Haplobunodon, 

 Lophiohunodon, Rhagatherium, — the Anoplotheriidae — Mixtotherium and the small 

 Leptotheridium, — and the first Xiphodontidae — Pseiidamphimeryx, Dichodon and 

 Haplomeryx. Rodents, Creodontia, and primates are by no means lacking, but 

 they are principally restricted to the Swiss Bohnerz. The American repre- 

 sentatives of this order have been more exactly studied. The primates found 

 in the Bridger beds are represented by the Nothardidae and the Anaptomorphidae, 

 the insectivores by the Pantolestidae, Hyopsodontidae, Mixodedidae, and by the 

 giant Tillotheriidae — Tillotherium — as well as by several small forms closely 

 allied to the Talpidae, Centetidae and Leptididae. The Miaddae develop the 

 greatest variety of species among carnivores — Viverravus, Miads, V'ulpavus. 

 The Oxyaenidae — Patriofelis, Limnocyon, Thinocyon — are likewise well represented, 

 and the 3feso7iydiidae during this period attain a specialization of the extremities 

 similar to that of present-day dogs. The primitive Hyaenodontidae — Sinopa 

 — are somewhat richer in forms here than in the Wasatch beds. The 

 same is also true of rodents, Paramys and Sduravus, to which several new 

 genera are added about this time. In North America, as is the case in 

 Europe, the perissodactyls become richer in forms in the Lower Eocene ; the 

 number of species of the Tapiridae, — Helcdetes, Isedolophus — and of the Equidae 

 — Orohippus — remains approximately the same, but the Titanotheriidae — 

 — Palaeosyops, Limnohyops, Telmatherium — become more varied in form. The 

 artiodactyls are represented only by Dichobunidae, which, however, manifest a 

 greater wealth of forms — Homacodon, Sarcolemur, Helohyus— than in the 



