40 FOSSIL TURTLES OF NORTH AMERICA. 
Slope are found two species of the Chelonidz and fragments of three species of 
Trionychida. We can not doubt that in the streams of the Mississippi Valley and 
eastward there was an abundant population of water-loving turtles, but farther 
westward this order of reptiles was represented principally by the land tortoises. 
During the Pliocene the land tortoises continued to predominate, especially in the 
interior region. [hree species are known trom the Blanco beds of Texas. In deposits 
of apparently the same age in Oregon there has been found a species of Clemmys. 
In the Peace Creek beds of Wionea: belonging apparently to the Upper Pliocene, 
there are found, with one large T estudo, numerous Emydidz and a species of 
Chelydride. These are closely prelate to Species } yet living i in that region. Among 
the numerous turtle bones put in the writer's s hands foil Hillsborough County, 
Florida, are many fragments that evidently belonged to yet undescribed species of 
Emydide and Triony chide. 
In the scattered deposits of the Pleistocene, 1 in which we might expect to find 
remains of turtles, we discover a few species; and these present a astill closerapproach 
to those now inhabiting the same territory. In what probably corresponds to the 
Equus, or Sheridan, beds of the region west of the Mississippi River have been 
discovered a species of Chrysemys, 3 species of Trachemys, a species of Terrapene, 
and 3 species of Testudo. It is worthy of note that no Tee aera the size 
that was reacht by species of the genus during the Miocene and the whole of the 
Pliocene. In the Atlantic region, in caves and superficial deposits, have been found 
remains of the snapping- iretles the sculptured turtle, another supposed species of 
Clemmys, and one or more species of box-tortoises. 
Briefly let us consider the geological history of the turtles of other regions. 
The earliest known turtle remains have been found in the Middle Tiaesies the 
Muschelkalk, of Germany. Huene (Palzont. Abhandl., x, 1906) has described 
a few cervical vertebra which he regarded as probably having belonged to crypto- 
diran turtles. In the Upper Triassic of the same country, the Keuper, has been 
found Proganochel ys, a nearly complete shell of which has been described by E. Fraas 
(Jahresh. V er. Naturk. Wiirrt., Lv, 1899, p. 401). The present writer believes that 
this turtle belonged to the Amphichelydia, and it is probable that the cervical 
vertebra from ae Muschelkalk belonged to some turtle of the same group. 
The next oldest known turtle, known only from impressions of the carapace on 
slabs of rock, is Protochelys strickland1, from the Stonesfield slate, of the Great 
Oolite, of Oxfordshire, E ngland. It belongs probably to the Amphichelydia. 
In contrast to the scanty chelonian population of the North American Upper 
Jurassic, that of Europe was extremely numerous. From the Jurassic at Solothurn, 
Switzerland, about 15 species have ‘been described. From deposits of approxi- 
mately the same age in Germany, France, and England, numerous other species 
have been reported. Many of the species have come from the Kimeridge, of the 
upper portion of the Great Oolite, a formation found in England, France, and 
Germany, and belonging near the level of the Morrison beds of Wyoming, as 
already stated. The principal g genera described from the Upper Jurassic of Europe 
are Ple urosternon, Plat yc helys, IB le stochelys, Idioc helys, Hydr opelta, Parac helys, 
Acichelys, Thalassemys, Ste gochelys, and Tropodemys The first two belong 
without doubt to the Amphichely dia, Pleurosternon being closely related to Glyptops 
and Platychelys to Probaéna. Craspedochelys and Ple siochelys are almost certainly 
not Pleurodira and may be referred provisionally to the Amphichelydia. The 
other genera are to be referred to the Thalassemydida, a family of Cryptodira. 
Sais turtles are found a little higher up in the European Jurassic, 1 in the Purbeck 
