24 THE SAUROPOD DINOSAUR BAROSAURUS MARSH. 
Measurements of Caudal III 
Barosaurus Diplodocus 
lentus carnegiei Ratios 
mm. mm. 
Length over all 236 278* 0.85 
Height over all 70s 92of 0.77 
Width across diapophyses 560 670! 0.84 
Centrum, anterior face, height 242 324* 0.75 
" width 34s % 
" circumference 965 t 
posterior face, height 190 27st 0.69 
" width 340 3351 1.01 
Pleuroccele, length ca. 100 
height 60 
Neural canal, height at anterior face 30 
width 43 
Width across pedicels " 220 
Width across postzygapophyses 930 
Neural spine, width (least) 72.8 
" " width of summit no 
Diapophysial lamina rugosity, length 280 
" " " width ca. 70 
Postspinal lamina rugosity, vertical length 360 
Average ratios : Barosaurus lentus and Diplodocus carnegiei 0.82 
* Calculated from photograph. 
t Peterson's measurements. 
fBone coossified with II in D. carnegiei, hence no measurement. 
The postzygapophyses are supported by a median bracket-like buttress which arises 
above the neural canal and bifurcates, one branch going to each zygapophysis. The 
latter face downward and outward at an angle of 45 degrees, so that their faces are at 
right angles to each other. The left facet is nearly flat, while the right curves through 
90 degrees of arc. From the postzygapophyses, strong but thin buttresses arise to 
reinforce the lateral margins of the neural spine (postzygapophysial laminae). There 
are also broad, horizontal ridges from the inner face of the postzygapophyses which 
converge upon the spine. (See PL V, Fig. 3.) 
The centrum of the specimen of Diplodocus longus in the American Museum of 
Natural History is more nearly circular, those of D. carnegiei and Barosaurus agreeing 
in proportions, hence probably more nearly normal. The main distinction of the Baro- 
saurus caudal III, aside from its smaller size, seems to be the non-cleft spinous process, 
which is slightly bifid in both species of Diplodocus. 
Caudal IV {Vertebra G) . — This bone is well preserved, save that the diapophyses 
are lacking with the exception of the upper portion of the right. 
Anterior face. — The centrum seems larger than that of caudal III and the pre- 
zygapophyses are heavy and wider apart. It is probable, however, that crushing has 
somewhat exaggerated this. The concavity of the anterior face of the centrum is also 
greater than in III. There is little to distinguish this bone from its predecessor. 
Lateral aspect. — The spine in its present condition slants somewhat more than in 
caudal III. The pleuroccele is large, and very deep, and lies in the upper half of the 
centrum. 
Rear aspect. — Centrum somewhat crushed. Width of neural canal at posterior end, 
50 mm. ; its height, 50 mm. 
