0. C. Marsh—Jurassic Bird from Wyoming. — 8.41 
Art. XLIL.—Discovery of a Fossil Bird in the Jurassic of 
Wyoming; by O. C. MARSH. 
THE oldest Birds hitherto known from American strata are 
the toothed forms (Odontornithes), from the middle Cretaceous 
deposits, on the eastern flanks of the Rocky Mountains. In 
Europe, three specimens of the genus Archeopteryx have been 
found in the Jurassic, but from older formations no remains of 
this class have been brought to light. The writer has made a 
careful search for fossil Birds in the Jurassic beds of the West, 
and has been rewarded by the discovery of various remains, 
some of which are sufficiently characteristic for determination. 
The most important of these specimens is described below: 
Laopteryx priscus, gen. et sp. nov. 
type specimen of the present species is the posterior 
bones of the skull are pneumatic. e occipital condyle is 
sessile, hemispherical in form, flattened and slightly grooved 
e is no trace of a posterior groove. e foramen 
magnum is nearly circular, and small in proportion to the 
condyle. Its plane coincides with that of the occiput, which is 
slightly inclined forward. The bones around the foramen are 
firmly codssified, but the supra-occipital has separated some- 
What from. the squamosals and parietals. Other sutures are 
more or less open. On each side of the condyle, and some- 
what below its lower margin, there is a deep rounded cavity, 
perforated by a pneumatic foramen. 
The cavity for the reception of the head of the quadrate is 
oval in outline, and its longer axis, if continued backward, 
would touch the outer margin.of the occipital condyle. This 
cavity indicates that the quadrate had an undivided head. The 
braincase was com aratively small, but the hemispheres were 
well developed. hey were separated above by a sharp mesial 
crest of bone. A low ridge divided the hemispheres from the 
optic lobes, which were prominent. 
e following measurements indicate the size‘of the specimen : 
Width of skull across occiput (approximate) -_----- 240m 
Transverse diameter of occipital condyle, .--- .--. -- 5 
Vertical diameter, 25262267. Ae ee 4 
Width of foramen magnum, -.--...-.------------ 5° 
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