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FOSSIL VERTEBRATES —REPTILIA 729 
form of the reptiles, and from them are probably derived the 
majority of the reptilian orders. They are characterized by a 
very generalized structure of the skull and skeleton that in many 
regards closely approximates the condition of the Asmphibia. 
The bones were not completely ossified; there were many 
abdominal ossicles, and the vertebre were perforated for the 
passage of the notochord. The group is extinct. 
Paleohatteria, the earliest of the order, is found in the Roth- 
liegende, Upper Permian, deposits of Niederhasslich near Dres- 
den. It was a small lizard-like animal about a foot long; the 
teeth were small and conical, and were developed on the vomer 
and palatine bones of the mouth as well as in the jaws, a char- 
acter common in the Amphibia. 
Proterosaurus is another form much longer and more slender, 
about six feet in length. It is peculiar in the fact that the 
vertebree of the neck are only seven in number, and are greatly 
elongated, as is common in the long-necked mammals. It is 
from the Keupferschiefer of Thuringia. 
Mesosaurus, from the Permian or Permo-Triassic of South 
Africa, is represented by the impression of the anterior half of 
an animal that was much like the Plesiosaurs in general appear- 
~ance; the neck was long and slender, and the head had the same 
kind of teeth. The posterior portion of an animal that is regared 
as belonging to the same genus has been found in the Permian 
of Brazil. 
RHYNCHOCEPHALIA. 
The members of this order differ only in degree from the pre- 
ceding. The bones are better ossified; the abdominal ossicles are 
reduced in number and simplified in arrangement; the noto- 
chordal opening in the vertebra is smaller and the skull has 
advanced toward the modern type of the reptiles. The group 
is of great importance, both because of the variety of the forms 
produced and because it is in all probability the direct ancestor 
of the later reptiles. The living Lacertiha and Ophidia, and, in 
all probability, the Zestudinata, as well as the extinct Plesc- 
osaurs, Icthyosaurs, Pythonomorpha, Pterosauria, Dinosaurs, Croco- 
