MORPHOLOGY OF BAROSAURUS LENTUS. 
17 
pleurocoele as seen from the side. In Brontosaurus also the hypantrum first appears 
on the fourth dorsal. The pleurocoele in Barosaurus is bounded above by a thin lamina 
of bone running to the upper margin of the rib facet, whereas in Diplodocus this 
lamina is unrepresented, the bone being thickly rounded where it would lie. 
From the anterior aspect (PI. Ill, Fig. 4) the bone exhibits an oblique crushing, 
but is otherwise intact except for a portion of the margin of the articular face. The 
latter is still decidedly convex. Above the neural canal rises a vertical lamina which 
supports, bracket-like, a shelf which in turn connects with the two prezygapophyses. 
From each of these arises a lamina (prezygapophysial lamina) which buttresses the 
anterior face of the neural spine, but fades out below the level of the crest. The 
median roughening for tendinous attachment, the prespinal lamina, extends from the 
neural cleft downward to the connecting shelf, a distance of 150 mm. The width of 
the spine at the level of the cleft is 190 mm. 
The posterior aspect (PI. Ill, Fig. 5), as has been said, is the first to show the 
hypantrum. This conforms with the hyposphene of the next vertebra to be discussed, 
which can not be forward of the fifth in series. The centrum face is well preserved 
and is markedly concave. The hypantrum is supported from below by a single bracket- 
like lamina which arises from the neural canal, where it bifurcates to form an arch 
over the opening. There are some depressions on the anterior face of the expanded 
portion of the bone just beneath the zygapophyses, but no distinct buttresses arise, as 
they would doubtless have impeded the intervertebral motion. The rugose postspinal 
lamina is of less vertical extent than the prespinal, but is more prominently raised 
above the level of the bone. Its vertical extent is about 80 mm. The diapophyses are 
strong and broad and well supported by the diapophysial lamina;. 
Measurements of Dorsal IV 
Barosaurus Diplodocus 
lentus carnegiei Ratios 
mm. mm. 
Length over all 290* 260* 1.11* 
Height over all 76of 770§t 0.99 
" to base of cleft 543 
Width across diapophyses 75°§ 
Centrum, length 260 240! 1.08 
" anterior face, height 220 250S? 0.88 
" " " width 290 278§ 1.04 
" circumference 880 
" posterior face, height 23s 27S§ 0.85 
" width 330 33511 0.98 
" " " circumference 920 
Neural canal, height 40 
" width 48 
Width across prezygapophyses 265 
Width across postzygapophyses 300 
Postspinal lamina rugosity, vertical length 80 
Average ratios : Barosaurus lentus and Diplodocus carnegiei 0.99 
* From photograph. 
t Estimated. 
J718 (Hatcher). 
§ Peterson's measurements. 
II Somewhat abnormal due to crushing (Peterson). 
