82 Saurians of the Dakota Beds of Colorado. [¥ebruary, 
The lightness of construction 
ofthe vertebrz of this genus is as 
remarkable as in the Camarasau- 
rus, but is differently exhibited. 
The greater fore and aft extent 
is seen in the fossz, which are 
therefore not so deeply excava- 
ted as in that genus, but the os- 
seous walls are not less lightened 
and attenuated. The elevation 
Jof the middle line of the back 
must have been extraordinary in 
the Amphicelias altus (Figs. 13, 
tthe sum- 
=_= 
we 
= 
Sa 
mit of the neural spine indicates 
the strength of the longitudinal 
ligament which connected the 
vertebræ with each other and 
with the head. 
The femur of Amphicælias 
altus is remarkable for its slen- 
der form. It is a few inches 
longer than that of the Cam- 
arasaurus supremus, but is not 
so robust. The shaft is nearly 
round and somewhat contracted 
at the middle, where it is slight- 
ly convex backwards. It is 
slightly curved inwards at the 
great trochanter. Here the shaft 
is moderately grooved on the 
posterior face. This trochanter 
is only a prominent ledge below 
the head. The third trochanter 
is situated a little above the mid- 
dle of the shaft; it is a promi- 
nent obtuse ridge directed back- 
wards. The condyles are €X- 
tended well posteriorly, and arè — 
= “/ separated by a deep popliteal 
Saaana --* proove, which originates on the 
Fig. 15—Femur of Amphicelias altus, Seen from the inner posterior direction, 
