446 Mesozoic and Cenozoic of North America. [ May 
The primary systems of the Mesozoic are four, viz.: 
Postcretacic, 
Cretacic, 
Jurassic, 
Triassic. 
TRIASSIC SYSTEM. 
The vertebrate fauna is characterized by the presence of Rep- 
tilia Belodontidz*® and Aétosauride, and of Mammalia Droma- 
theriidz ;9 also by the absence of Dinosauria Opisthoccela,? 
Orthopoda, Parasuchia,* and Eusuchia; of Batrachia Anura and 
Urodela; of Saurodont and of Physoclystous fishes. 
The division of the Trias into Muschelkalk and Keuper, so 
well marked in Europe, is not distinguishable in North America, 
our beds presenting the faunal characters of the Keuper or 
. upper Trias of that continent. They, however, present two 
divisions which are lithologically distinct in Nevada, to which 
Mr. King” has given the names Koipato for the lower and Star 
Peak to the upper. The latter is of marine origin, while the 
Trias of the Rocky Mountains and of the Atlantic slope is la- 
custrine. The Rocky Mountain Trias is exposed upturned along 
both the eastern and western slopes of north and south ranges, 
and the north and south slopes of east and west ranges. In 
Nevada it forms the mass of the Havalla, Pah Ute, and West 
Humboldt ranges. Its thickness is, according to King,— 
Colorado, east flank of n mountains 309 to 1200 
Nevada, Koipato bed 4000 to 6000 
- Nevada, Star Peak bed 10,000 
Triassic beds probably also occur in the Indian Territory.* 
JURASSIC SYSTEM. 
The vertebrate fauna is characterized as follows: 
Present: Reptilia Dinosauria Opisthoccela, Orthopoda, Meso- 
suchia; Testudinata Clidosterna; Ichthyopterygia Sauranodon- 
tide ;* Batrachia Anura; Mammalia ?Bunotheria Absent: 
Pisces Actinochiri, TRAE NTAN Percomorphi; Dinosauria 
Belodontidæ ; Reptilia Ch ecletsderes ;5 Aves Odontornithes ; 
: Mammalia Placentialia Ungulata, Creodonta, and Tillodonta. 
= * Triassic formations have not yet been detected in Texas, those recently referred | 
by Mr Hill of the United States Geological Survey to that age being the Permian 
of the Red River. Se ee 302.) 
