MORPHOLOGY OF BAROSAURUS LENTUS. 31 
whether the two ridges had coalesced to form a single roofing is not quite clear. The 
latter, however, I believe to have been the case. Viewed from either side, the perfora- 
tions are quite symmetrical. I have no idea as to the cause of this seemingly unique 
phenomenon. The entire bone, viewed from either front or rear, is curiously asym- 
metrical, as were the vertebrae. (See Text Fig. 4.) 
Measurements of Chevron ca. IX 
Barosaurus 
lentils 
mm. 
Length 243 
Width of base 136.7 
Anteroposterior diameter of blade 55.5 
Haemal canal, height 67 
" " width 44 
Chevron ca. XVI (PI. VI, Fig. 7; Text Fig. 5). — A third chevron is present, 
admirably preserved except for the extreme anterior point. This bone is elongated in 
its antero-posterior diameter and hence presents a very different appearance from those 
/ 
he 
Figure 4. — Chevron ca. IX, rear aspect. One-fourth natural size. Note 
the decided asymmetry, he, haemal canal; c, crease; p, perforation, see 
text. 
which have been described. It differs in shape, moreover, from any of those preserved 
with the American Museum specimen (vide supra, preface) in that the ascending portion 
is proportionately somewhat heavier than the fore and aft extensions. 
The base is heavy, with large facets, of which the lesser forward area is perhaps 
three-fifths as great as the posterior. 
The bone shows little asymmetry as contrasted with that just described (compare 
PI. VI, Figs. 6 and 7). The margin of the posterior extension rises in a gentle curve 
into that of the base; the anterior margin, on the other hand, is much more abruptly 
curved, as the figure shows. Ventrally, there is an elongated, alveolus-like depression 
(Text Fig. 5 B, a), forerunner of the median opening which, in the more posterior chev- 
rons of Diplodocus? separates the bone into a pair of slender rods. This alveolus-like 
Osborn, op. cit., p. 209. 
