516 O§fC. Marsh—New Dinosaurian Reptiles. 
the middle part being so diminished as to greatly reduce the 
strength. The vertebra preserved are biconcave, with shallow 
cavities. The feet bones referred to this species are very 
slender. A lumbar vertebra has its centrum 105 mm. in 
length, and 89 in least transverse diameter. An anterior 
caudal, 35 mm. long, has its centrum so much cae ied that 
its least transverse diameter is 38 mm., while its anterior face 
is 90 mm. in transverse diameter. 
The animal indicated by the remains preserved was from 
fifteen to twenty feet in length. All the known specimens are 
from the upper Jurassic of Colorado. 
Nanosaurus rex, sp. nov. 
A diminutive Dinosaur, about as large as a fox, is indicated 
by some remains in good preservation, the most characteristic 
of which is a nearly perfect femur. In this bone, the great 
trochanter is prominent, and the third trochanter especially sO. 
There is a well developed fibular ridge, directed outward and 
backwar "be cavity in this bone is unusually large, and the 
walls are smooth. This femur agrees so nearly with that of the 
type of Nanosaurus, that the present species may be provision- 
ally referred to that genns. 
e dimensions of this bone are as follows: 
Length of fem TOR = 
Distance from head to middle ‘of third trochanter . = 30° 
Transverse diameter of distal end __._......-.---- 21 
Great ro-posterior diameter ...-.--.-...--- 18 
Least transverse diameter of shaft_....._...___--- 11 
Diameter across third trochanter__...... ....-.--- 15° 
The known remains of this reptile are from the upper 
Jurassic of | Colorado. 
The specimens described in the resent articles are deposited 
in the Peabody Museum of Yale Co ollege. They are all from 
essentially the same geological horizon, which I find to be upper 
Jurassic. The deposits which contained them may be called 
the Atlantosaurus beds, from their most characteristic fossils, 
the huge Dinosaurs of that genus 
Yale College, New Haven, November, 1877. 
