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O. C. Marsh—Extinct Jurassic Reptiles. 341 
i Art. XXXIX.—A new order of extinct Jurassic Reptiles » 
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MACELOGNATHA); by O. C. Mars 
A NEW type of reptilian life is represented in the Yale 
Museum by various remains, the most characteristic of which 
are the two dentary bones of the lower jaws. These bones 
resemble in many respects the corresponding parts of a Turtle, 
but are broader, and more nearly horizontal. The jaws were 
evidently covered with a horny beak in front, but further back 
they contained teeth. The edentulous portion is flat and thin, 
a and nearly horizontal. The two rami meet in nearly the same 
oie and are united at the symphysis by a close suture. The 
form and general characters of these specimens are represented 
in the eut below. 
Jaws of Macelognathus vagans, Marsh. Seen from above. One-half natural size. 
The teeth were implanted in distinct sockets, in front, but 
further back, the walls between them become thinner, and a 
groove appears to gradually take their place. The form of 
the teeth cannot be d 
d r Ptero- 
dactyles. With Serpents and Lizards they have evidently 
only remote affinities. The close union of the rami by suture 
separates them from the Dinosaurs, and the endentulous beak, 
from Crocodiles. So far as now known, they appear t 
ar to be 
nearest allied to the Chelonia, although Turtles without teeth 
occur in the same strata wit m. 
The geological horizon of these peculiar remains is in the 
Atlantosaurus beds of the Upper Jurassic. The locality is 
in Wyoming Territory. 
Yale College, March 21st, 1884. 
Am. Jour. jon Dee Serres, VoL. XXVII. No. 160,—ApRIL, 1884. 
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