MESOZOIC. 261 
[Note. — If the question in regard to names is not already set- 
tled, I should earnestly advocate the transposition of the terms 
Group and Series, so as to have Series used for the names of the 
first order, and Group for those of the third order. This use of 
the words is nearer in accordance with the present usage of Eng- 
lish-speaking geologists.] 
MESOZOIC REALM.* 
By Prof. Cope. 
This system is distinguished from the Paleozoic in North 
America, as to the Yertebrata, as follows : 
Presence of Peptilia Dinosauria, Ichthyopterygia, Sauropte- 
rygia? Pterosauria, Testudinata, and Lacertilia; presence of 
Mammalia. Absence of Tunicata Antiarcha, Agnatha Arrhina, 
and Diplorhina, of Pisces Placoganoidei, of Batrachia Ganoce- 
phala? Rhachitomi and Embolomeri, and of Reptilia Thero- 
morpha. 
From the Cenozoic system the Mesozoic differs in the pres- 
ence of Reptilia Dinosauria, Sauropterygia, Ichthyopterygia ; of 
Mammalia Marisupialia Multituberculata ; and in the absence 
of Pisces Actinopteri, Nematognathi, and Plectospondyli ; of 
Aves Insessasores, and Mammalia Diplarthra and Rodentia. 
The primary systems of the Mesozoic are four, viz.: 
Postcretacic, 
Cretacic, 
Jurassic, 
Triassic. 
TRTASSIC SYSTEM. 
The vertebrate fauna is characterized by the presence of Rep- 
tilia Belodontidfe and Aetosauridse, and of Mammalia Droma- 
theriidse ; also by the absence of Dinosauria Opisthoccela, 
Orthopoda, Parasuchia, and Eusuchia; of Batrachia Anuria 
and Urodela ; of Saurodont and of Physoclystrous fishes. 
The division of the Trias into Muschelkalk and Keuper, so 
well marked in Europe, is not possible in North America, our 
* Prof. Cope objects to the adoption of the word " group," as proposed by the 
Congress of Berlin, for the division of geological formations of the first rank, 
and proposes to substitute the word "realm" therefor; e.g., the Archean, 
Paleozoic, Mesozoic, and Cenozoic Realms. — American Naluraliif, 1887, p. 445. 
