24 
PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
not been preserved in the anterior cervicals available for study. In the 
sixth, the transverse process supports a large hatchet-shaped inferior lamina 
and a prominent diapophysis. The former is wanting in the seventh 
cervical and the diapophysis is greatly elongated. 
No complete dorso-lumbar series is known, but, from analogy with the 
closely related Inter atherium, it may be assumed with a high degree of 
probability that there were fifteen dorsals and seven lumbars. The anter- 
ior dorsals (PI. VI, fig. 8) have high narrow spines strongly inclined 
backward, with the tips terminating in knob-like expansions. The spines 
of the posterior dorsals (PI. VII) are wide antero-posteriorly, with 
obliquely truncated, dorsally flattened summits. The change from back- 
ward to forward inclination of the neural spines occurs at about the thir- 
teenth dorsal. The spines of the anterior lumbars resemble those of the 
posterior dorsals, but increase in length and are more slender posteriorly. 
The transverse processes of the lumbars are broad flat blades, curving 
forward and downward. The width of these processes increases in the 
posterior lumbars. Prominent anapophyses are developed in the posterior 
dorsals and anterior lumbars, but decrease in size toward The end of the 
lumbar series. Large metapophyses and strongly interlocking zygapoph- 
yses are also characteristic of the posterior dorsals and lumbars (PI. VI, 
figs, io, 14, 15). 
Three sacrals are in contact with the ilium and two caudals are fused 
with them, making five vertebrae in the sacral complex (PI. VI, fig. 10). 
A dorsal intervertebral fenestra is present between the first and second 
sacrals. The remaining sacrals and the first and second caudals have the 
neural arch firmly fused, without trace of fenestrae. The neural spine of 
the first sacral is imperfectly preserved, but appears to have been similar 
to that of the posterior lumbars. The spines of the remaining members 
of the caudo-sacral series are solidly fused, as in Interatherium , forming a 
narrow plate, with the dorsal margin transversely expanded and flattened. 
The tail is known to have been long, eighteen free caudals being pre- 
served with one specimen (No. 15,161). The proximal caudals have broad 
transverse processes and short, transversely compressed spines. Pos- 
teriorly, the spines rapidly decrease in height and the transverse processes 
elongate antero-posteriorly, but decrease in transverse diameter. Begin- 
ning with the seventh free caudal, the neural arch is greatly reduced and 
the transverse process limited to a small tuberosity at the anterior and 
