1 8 THE SAUROPOD DINOSAUR BAROSAURUS MARSH. 
Dorsal V {Vertebra L) (PI. IV, Figs. 1-3). — This bone is fairly well preserved 
except for the neural spine and diapophyses. The centrum, as usual, is obliquely 
crushed, so that the anterior face of it has been shifted' to the left. This is the first 
vertebra to show the hyposphene or anterior accessory articulation, dorsal IV showing 
but the hypantrum. In dorsal V, the entire articulation is very massive and well 
buttressed. This vertebra also shows a cleft spine, but the bottom of the cleft is very 
materially higher than in the fourth. The capitular rib facets are now clear of the 
centrum, being borne entirely upon the pedicel of the neural arch; they are, however, 
lower than in the corresponding bone of Diplodocus. The two laminae which support 
the prezygapophyses (prezygapophysial laminae) have their origin in the rib facet and 
transmit a thrust direct from rib to zygapophysis. The centrum is as deeply 
opisthoccelous as are its predecessors. 
Two laminae, as before, arise from the shelf between the zygapophyses and run 
upward, diminishing as they go ; then, becoming accentuated again as the spine becomes 
lightened, they exhibit the marked asymmetry to be emphasized in vertebrae VII and 
IX (see below and PI. IV, Figs. 1, 3). The tendinous roughenings, the pre- and 
postspinal laminae, are not very pronounced, but run up the entire face of the spine to 
the base of the cleft. 
Lateral aspect (PI. IV, Fig. 2). — The pleurocceles are apparently very deep but 
are filled with matrix. They are proportionately but slightly smaller than in dorsal V 
of Diplodocus. The capitular facets overhang them slightly and look somewhat down- 
ward and backward. The diapophysis is well supported, as the thin anterior and 
posterior diapophysial laminae buttress it from below, and it is connected with the 
prezygapophysis by the horizontal lamina. Of the diapophysial laminae the anterior 
one arises just above the rib facet, the posterior one nearer the hinder margin of the 
centrum, the two converging beneath the diapophysis. Between the anterior diapophy- 
sial, the horizontal, and the oblique laminae of the prezygapophysis there is a very deep 
depression, extending nearly to the central plane of the bone. 
The posterior aspect (PI. IV, Fig. 3) is very well preserved and has suffered less 
from crushing than has the anterior face. The centrum shows, in its present condition, 
less concavity than that of dorsal IV and less than the immediately succeeding ones. 
Two of the latter have suffered lateral crushing instead of the antero-posterior shearing 
strain as in the present instance, which probably accounts for their increased curvature. 
The neural arch is narrowest across the pedicels, above which it expands very 
widely to support the diapophyses, the surface of the bone showing but few inequalities. 
There arises a median buttress, the postzygapophysial lamina, just above the neural 
canal. This increases in width from nothing to 9.6 mm. as it rises. The average 
width of the buttress, however, is but 8 mm., except just beneath the hypantrum. 
The height of the zygapophysis above the centrum is about 240 mm. Greatest width 
across hypantra, 93.5 mm. ; least, 23.5 mm. Greatest width across zygapophyses, 
265 mm. 
There is a curious asymmetry in the spine as viewed from the rear, in that on the 
left side there is a large oval depression (PI. IV, Fig. 3, D) about 60 mm. wide, which 
is almost entirely lacking on the right. The rugose postspinal lamina is pronounced, 
and while it rises but little above the general level of the bone, it has a length of 188 mm. 
