514 O. C. Marsh—New Dinosaurian Reptiles. 
indebted to Prof. A. Lakes and Engineer H. C. Beckwith of 
th avy, who found the first remains in Colorado near 
the locality of the gigantic Adlantosaurus montanus, and in 
essentially the same horizon. 
Yale College, New Haven, Nov. 15th, 1877. 
Art. LITI.— Notice of New Dinosaurian bees lates the Jurassic 
jormation ; by Professor O. C. M 
THE gigantic Dinosaur, Atlant montanus, described by 
the writer in the July number of this Je ee * proves to belong 
to a lower horizon than at first supposed, and is really from the 
upper Jurassic. Additional remains of the type specimen, 
moreover, throw considerable light on the structure of this 
largest of land animals, and indicate that it is the representa- 
tive of a distinct family, which may be called Atlantosauride. 
In the type genus, Atlantosaurus, one of the most important 
characters is the pneumaticity of the vertebre, as mentioned in 
the original description. Another noteworthy feature is the 
absence on the femur of a third trochanter. The shaft of the 
one is somewhat thickened at the point where this process 
should be, but the trochanter is wanting. The size of the orig- 
inal specimen of A. montanus may be estimated from the femur, 
which was about seven feet in length. If the animal had the 
proportions of a Crocodile, it was at least eighty feet long. 
Apatosaurus ajax, gen. et sp. nov.t 
Another gigantic Dinosaur, allied to the above, and of 
scarcely less interest, is represented i in the Yale Museum by a 
nearly complete skeleton in excellent preservation. It is from 
the Jurassic beds in the Eastern foot hills of the Rocky Moun- 
tains, but from a somewhat lower horizon than the type 
of Atlantosaurus. 
the centra. The anterior dorsals have stings shan ter The 
posterior lumbars have the articular faces very nearly flat, and 
transverse. The sacral vertebra are more solid, and have ‘their 
transverse processes nearer the middle of the centra than in 
Atlantosaurus. The anterior caudals are biconcave, and their 
* Vol. xiv, p. 87, 1877. The name Titanosawrus was first given, but, being pre- 
occupied, may be replaced by Adlanto: — 
¢ The principal chatunides | of this genus and its nearest allies were given by the 
writer in a paper before the Wotiinal 1 pt of Science, at the meeting in New 
York, October 25th, 1877. : _ 
