Diplodocus 
carnegiei 
Ratios 
mm. 
S90t 
1.62 
». S8st 
S20t 
I.46 
590t 
1.22 
233f 
0.86 
2S5t 
i-43 
759 
1.27 
352 
1.27 
1.30 
MORPHOLOGY OF BAROSAURUS LENTUS. 15 
Measurements of Cervical XV 
Barosaurus 
tcntus 
mm. 
Length over all 060* 
Height ov^r all 
Width across diapophyses 760 
Centrum, length 720 
" posterior face, height 200* 
" width 365 
" " " circumference 970 
Pleuroccele, length ca. 160 
Prezygapophysis to rib facet 450 
Average ratios: Barosaurus lenius and Diplodocus carnegiei 
* Probably exaggerated by crushing. 
* Furnished by Peterson. Other measurements from figures. 
DORSAL VERTEBRAE 
Dorsal I (Vertebra P) (PI. Ill, Figs. 1-3). — A fairly well preserved bone. Such 
portions as are lacking on one side, however, are fortunately preserved on the other. 
As compared with the fifteenth cervical, the first dorsal is much shorter, the centrum 
of the latter measuring but 470 mm., as against the 720 mm. of the former, nor are the 
anterior wing-like expansions — horizontal lamina; — of so great antero-posterior extent, 
although their over-all width is nearly as great. The centrum shows much the same 
curvature of articular ends as does that of cervical XV, which is also true of their obliq- 
uity, especially of the posterior face. This obliquity is markedly greater than in Diplo- 
docus carnegiei, and while doubtless due in part to crushing, as in cervical XV, it also 
seems to indicate a greater vertical flexion than is usual with sauropod dinosaurs. The 
seventh cervical of the Camelidse is similarly modified, and also shows, in the llama at 
least, a marked dorso-ventral flattening of centrum similar to that of the first dorsal of 
Barosaurus. The convexity of the anterior face of the present bone is considerably less 
than in Diplodocus, but herein again the bone may not be quite normal. It may, how- 
ever, be correlated with less mobility of movement at this point. 
The pleurocceles are relatively much larger than in the cervicals, occupying approxi- 
mately one-half of the centrum length. Their depth is also great, although its precise 
limit may not be ascertained, as the median separating wall has been destroyed and the 
two pleurocceles are confluent. Above, the pleuroccele is bounded by a thin, horizontal 
lamina of bone which serves to buttress both articular faces as they expand, the centrum 
being markedly constricted in the middle portion. 
The prezygapophyses are wide, more like those of the cervicals, while the 
postzygapophyses are more dorsal-like, although with as yet no trace of the hyposphene- 
hypantrum articulation characteristic of the later dorsals. Width of the right 
prezygapophysis, measured on the curve, 230 mm.; of the left, 240 mm., showing the 
asymmetry characteristic of these forms. Length of the left postzygapophysis, the 
one preserved, 140 mm. There is the same nodular insertion for a longitudinal tendon 
lying at the bottom of the cleft of the neural spine as in the cervicals. A continuation 
of this nodule extends downward on the rear side of the bone as a distinct ridge, the 
