12 THE SAUROPOD DINOSAUR BAROSAURUS MARSH. 
The prezygapophysis is preserved but displaced. Were it in its proper position, it 
would add considerably to the over-all length of the vertebra. The actual articular facet 
is very short antero-posteriorly, but wide transversely, and is somewhat convex upward 
in its transverse diameter. 
The postzygapophysial facet is similarly short and wide; it is, of course, concave 
downward and outward (see PL II, Fig. i, P. Z.). 
The neural spine in this and the succeeding vertebra is deeply bifid, with a median 
nodular excrescence for tendinous attachment at the bottom of the cleft. The spine 
rises about no mm. above the level of the tubercle on either side. The forward margin 
of the neural spine is continued as a thin ridge which forms a sweeping curve down to 
the prezygapophysis. The summit is somewhat thickened, and just beneath this 
thickening lie two pronounced cavities. A well defined posterior oblique lamina rises 
from the diapophysis and runs upward and backward to the superior limitation of the 
postzygapophysis. There is a distinct lateral depression just below this oblique lamina 
at its mid-length. The horizontal lamina is very pronounced, especially toward the 
diapophysis. It lies about at the level of the upper margin of the centrum. 
Comparison with Diplodocus carnegiei. 3 — In comparison with the twelfth cervical 
of Diplodocus carnegiei, this bone differs in its much greater size, as shown by the 
table of measurements below, that of Barosaurus being over 50 per cent larger, espe- 
cially in the central dimensions. The neural spine, however, is relatively somewhat 
lower. The pleuroccele of the Barosaurus cervical is much smaller relatively and is 
hardly as complicated; there is, however, the same oblique lamina dividing it into two 
portions, and in each instance this bifurcates anteriorly. One important difference lies 
in the position of the diapophysis, which in vertebra? XI and XII of Diplodocus carnegiei 
lies far forward, while in Barosaurus it lies more than one third of the distance back 
from the anterior end of the bone. Herein it resembles cervical X of Diplodocus much 
Measurements of Cervical XII 
Barosaurus Diplodocus 
lentus carnegiei Ratios 
.mm. mm. 
Length over all 1020 650* 1.57 
Height over all 560 490! 1.15 
Centrum, length 930 (6ooJ)-627* 1.48 
" anterior face, height 216 165$ 1.31 
" width 220§ 210J (1.05) 
posterior face, height 273 200$ 1.36 
" " " width 220 (228^-225* (0.98) 
" circumference ca. 800 70o|| 1.14 
Pleuroccele, height 60 
" depth ca. 50 
Index of total length to height 1.98 1. 14 
Average ratios: Barosaurus lentus and Diplodocus carnegiei 1.33 
* From Hatcher's measurements. 
fFrom two figures, photograph gives 703. 
t From O. A. Peterson's measurements. 
§ Crushed. 
|| From J. B. Hatcher's figures, all measurements not being given. 
3 J. B. Hatcher, Diplodocus Marsh, its Osteology, Taxonomy, and Probable Habits, with a Restora- 
tion of the Skeleton. Mem. Carnegie Mus., Vol. 1, No. 1, 1901, p. 24, Fig. 7. 
