524 Reviews—Prof. 0. C. Marsh’s 
the Stegosayria. Other Dinosaurs from the same horizon, the 
« Atlantosaurus beds,” show that this was the dominant form of 
vertebrate life in that age, and many hundred specimens of these 
reptiles are now in the Yale Museum. In a lower horizon of the 
same formation, the “Sauranodon beds,” were found the remains of 
a peculiar new group of reptiles, the Sauranodontia, allied to 
Tebthyosaurus, but without teeth. : 
In the Eocene deposits of the Rocky Mountains the writer dis- 
covered a new order of huge mammals, the Dinocerata. Remains of 
several hundred individuals were secured, and:a monograph on the 
group will follow the present memoir. In the same formation were 
found the remains of another new order of mammals, the Tillodontia, 
in many respects the most remarkable of any yet discovered. In 
the same Eocene deposits were secured the first remains of fossil 
Primates known from North America, as well as the first Chiroptera, 
and Marsupialia. Abundant material also was found in the same 
region to illustrate the genealogy of the Horse, and a memoir on 
this subject is in course of preparation. : 
The remains of birds are among the rarest of fossils, and very 
few have been discovered except in the more recent formations. 
According to present evidence, the oldest known birds were im- 
bedded in the Jurassic deposits of Europe, which have yielded two 
individuals belonging to the genus Archgopteryx, so well preserved 
that the more important characters can be determined. The only 
other remains of birds found in the Mesozoic formations of the Old 
World are a few specimens from the Cretaceous of England, which 
are too fragmentary to throw much light on the extinct forms they 
represent. 
The earliest traces of birds hitherto found in the strata of this 
country are from the Cretaceous, althongh we may confidently 
predict their discovery in the Jurassic beds, if not ata still lower 
horizon. There is at present no evidence whatever that any of the 
three-toed impressions met with so abundantly in the Triassic of the 
Connecticut Valley, described as the fovtprints of Birds, were made 
by Birds; and the proof now seems conclusive that nearly all of 
them are the tracks of Dinosaurian reptiles, bones of which occur 
in the same deposits. 
In the Cretaceous beds of the Atlantic coast, and especially in the 
Green-sand region of New Jersey, various remains of birds have 
been found, and described by the writer. These fossils, although 
often in excellent preservation, occur mainly as isolated bones, and 
hence their near affinities have not as yet been determined with 
certainty. 
Along the eastern slope of the Rocky Mountains, and especially 
on the adjoining plains in Kansas and Colorado, there is a series of 
Cretaceous strata remarkably rich in vertebrate fossils. The deposits 
are all marine, and away from the mountains, they lie nearly. 
horizontal. They have suffered much from erosion, and are still 
wasting away, especially along the river valleys. These beds 
consist mainly of a fine yellow Chalk and Calcareous shale, both 
