GEOLOGICAL DISTRIBUTION. 39 
similar that there 1s no wonder that the faunz did not ditter greatly. Inthe Laramie, 
as in the Judith River, there were Baénidz and Trionychide. The Dermate- 
mydidz are represented by at least one species, Basilemys sinuosa, not greatly 
different from B. vartolosa of the Judith River. The Pleurodira appear to be 
represented by one species, Natadochelys ingravata, from New Mexico. 
On entering the Tertiary there is no striking change in the turtle fauna. In the 
Fort Union, the Puerco, and the Vorrejon, ere are yet Prionychide, Dermate- 
mydidz, and Baeénidz. Representatives of the same families pass up into the 
Wasatch. Here, however, new elements enter, the Emydidz and the Testudinide. 
It is not improbable that Gyremys spectabilis of the Judith River beds is an emyd, 
but the group 1s unmistakably represented 1 in the Wasatch by Echmatemys, a genus 
in some respects highly specialized. ‘The Testudinidz are represented by the 
genus Hadrianus, the oldest-known genus of the family. All these Wasatch turtles 
inhabited either the land or the fresh waters of streams. 
In the Atlantic region we have nearly contemporaneous deposits; and in them 
we find fragmentary remains of a few probably marine turtles and of Trionychide. 
The Wind River beds have so far furnisht only a single species of Baptemys, and 
the humerus, 187 mm. long, of a trionychid. 
The Bridger beds of Wy oming are exceedingly rich in turtle remains, as they 
are also in ha bones of crocodiles and mammals. The Baénidz were numerous in 
species and individuals. Only 2 genera of dermatemyds have been found. Emy- 
did abounded, and Triony ines ran riot. In addition to these there were a few 
species of Plastomenide. All together, there are 50 or more species of turtles 
described from the Bridger Eocene. The abundance of Baénide and especially 
of the Trionychidze shows that there were numerous streams and lagoons; and this 
conclusion is confirmed by the presence of many species of eewendiles: ‘The occur- 
rence of the great turtle Hadrianus seems to indicate the proximity of dry land. 
Nearly calle the species of Bridger turtles occur in the lower portion, that known 
as level B. No turtles have yet been described from the limestone bands, but 
fragmentary remains occur there. These bands appear to have been laid down in 
Shaler lakes. 
So far as known the turtles of the Uinta beds belong to genera found in the 
Bridger beds. No Plastomenide have been found, and the Baénidz appear for the 
last time in our calendar. 
During the Oligocene epoch the scene, for the student of turtles, shifts from the 
sea shore and the mountain regions to the Great Plains. In the lowest division, the 
Chadron or Titanotherium beds, are found 1 trionychid, 1 dermatemyd, and 
1 emyd, silent witnesses of the presence of streams. On the other hand, there were 
numerous species of Testudinide, or dry-land tortoises, some of which attained a 
large size. Of Stylemys nebrascensis great numbers of shells have been found in 
Sauch Dakota and Colorado, in the Bale clays, or Oreodon beds. Species of 
T estudo were more abundant in the same deposits in Colorado. There can be no 
doubt that at this time the climate of the Plains region had become arid and the 
streams few. A similar climate appears to have prevailed in the John Day region 
of Oregon, where 2 or 3 species of Stylemys abounded, but, so far as iGroneh. no 
other turtles. 
The Miocene deposits of the interior of the continent are characterized by the 
presence of species of T estudo, many of them of large size, resembling the gigantic 
tortoises of the Galapagos Islands. Sixteen species are described. In the. “Middle 
Miocene of Oregon there has been found a species of Clemmys (C. saxea); 1n the 
Upper Miocene of Kansas, Trachemys hill. In the Yorktown beds of the Atlantic 
