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A NEW MYLODON. 
Parts of sixteen dorsal vertebrae are preserved, in some cases enough to re- 
construct nearly the entire bone. Vertebrae 8 to 13 are almost complete, but 
of the eight following, the centra and pedicle portion are broken or imperfect 
so that reconstruction is difficult. Probably there were sixteen dorsals. In 
Mylodon robustus there were sixteen pairs of ribs. 
The centrum of the first dorsal is roughly elliptical as seen from in front, 
with a transverse diameter of 59 mm., and a vertical of 40 mm., as measured 
on the articular surface. The posterior face is not so wide, and like the anterior, 
bears the demifacets at the sides. The pedicles rise from the anterior upper 
corners of the centrum, are short, thick, and oval in section. The cranial 
articular facets are broadly elliptical, with their long axes nearly transverse. 
The neural spine is some 145 mm. high from the anterior dorsal edge, thin and 
compressed, but with a greater width posteriorly, where it is ridged vertically. 
The summit is flattened, its sides diverging posteriorly to a width of 21 mm. 
In the succeeding vertebrae the centrum becomes more or less triangular in 
face view. ‘This is first observable in the next but one, (tenth), the posterior 
face of which is distinetly three-cornered with the ventral point rounded. The 
sides also are concave. In the sixteenth vertebra the centrum is largest and 
deepest (62 mm. anteriorly). 
With the eleventh vertebra the pedicle increases in length until it arises 
from nearly the whole side of the centrum; at the same time it becomes gradu- 
ally much reduced in thickness on successive vertebrae. The cranial demifacets 
of the ninth vertebra are borne on the anterior base of the pedicel; the caudal 
demifacets at the dorsal corner of the centrum. The tenth vertebra is similar 
but the cranial demifacets are more elongated vertically. In the eleventh 
they become lateral. The caudal demifacets are mainly borne by the posterior 
base of the pedicle, and seem to become obsolete at about the eighteenth ver- 
tebra. 
The transverse processes, so far as preserved, are at first broad and irregular 
in shape, with a prominent anterior point and two posterior ridges. A facet 
for articulation with the tubercle is present externally. Posteriorly on sueceed- 
ing vertebrae the two ridges lengthen and diverge forming a Y on the 14th to 
16th or 17th vertebrae. The inner fork of the Y at length becomes much the 
longer until finally it forms a ridge with an obtuse angle. The entire transverse 
process grows successively more elevated and longer, with a groove of increasing 
size that passes from the outer to the inner side of the ridge. 
The cranial articular facets of the 3d to the 8th vertebrae are all slightly 
