1877.] 245 [| Cope. 
the latter displays the usual form, that is, it is compressed in the direction 
of the axis of the column. The centra differ from those of Camarasaurus 
in the form of their articular extremities, resembling more nearly in this 
respect the genus Tichosteus Cope (Paleontological Bulletin, No. 26, p. 
194), They are unequally amphiccelous, the posterior extremity being 
more concave, and with prominent margins ; while the opposite one is 
less expanded and is but slightly concave. The neural arch is codssified 
to the centrum, and there is no capitular costal articulation on the latter. 
The manner of the mutual articulation of the neural arches in this genus 
is peculiar, and is only paralleled in the genus Camarasaurus, so far as I 
can ascertain. The anterior zygapophyses are separated by a deep fissure, 
while the posterior zygapophyses are united on the middle line. From the 
latter from the point of junction, there descends a vertical plate which 
rapidly expands laterally, forming a wedge whose base looks downward. 
The supero-lateral faces are flat, and articulate with corresponding facets on 
the inferior side of the anterior zygapophyses, which look downward and 
inward, on each side of the fissure above described. When in relation, the 
anterior zygapophyses occupy a position between the posterior zygapophy- 
ses above, and the hyposphen, as I have termed the inferior reversed 
wedge, below. This arrangement accomplishes the purpose effected by the 
zy gosphenal articulation, that is the strengthening of the articulation be- 
tween the neural arches, but in a different way. The additional articula- 
tion is placed at the opposite extremity of the vertebra, and it is the anterior 
zy gapophysis instead of the posterior one which is embraced. ‘This struc- 
ture entitles the genera which possess it to family rank, and as the two 
genera mentioned above belong to different families in consequence of the 
different types of vertebral centra, the one opisthoccelous, the other ainphi- 
ceelous, they may be called Camarusauride and Amphicaliidw respec- 
tively. 
The pubis is a stout bone with one slightly concave, thicker border, and 
an opposite strongly convex, thinner margin. One extremity is truncate ; 
the other presents one transversely truncate and one oblique face. The 
femur is elongate, and presents a strong postero-external ridge or third tro- 
chanter near the middle of the shaft. The head is not separated by a well 
marked neck, and the great trochanter does not project beyond it. 
Thus while there is a striking resemblance to Cumarasaurus in what 
may be regarded as adaptive characters, in some important essentials the 
two genera are very different. 
AMPHICGELIAS ALTUS Cope. 
Paleontological Bulletin, No. 27, p. 3. 
The centrum of the dorsal vertebra of this reptile is contracted both lat- 
erally and inferiorly, so that the margins of the articular extremities flare 
outwards. The sides are flat, and the inferior surface but little convex in 
the transverse direction. The pneumatic foramen issituated at the bottom 
of a large lateral fossa which extends nearly the entire length of the superior 
