HAPLODONTIDZ—VERTEBRA OF HAPLODON RUFUS. 5T5 
more obliquely forward, becomes more and more horizontal, and narrows in 
the fore-and-aft direction coincidently with its increase in lateral projection. 
Metapophyses, as distinct as those of the posterior dorsals, continue unchanged 
in appearance part way through the lumbar series. The long acute ana- 
pophyses which continue to be given off from the posterior extremities of the 
“transverse” processes gradually shorten to the 4th lumbar, and are abruptly 
suppressed on the 5th and 6th, where the “transverse ” process appears as a 
simple, faleate, acute process, projecting horizontally outward with strong 
forward obliquity. For the rest, the centra of the lumbars are stouter, with 
more hour-glass constriction than those of the dorsal vertebree, and the pinch- 
ing of their sides develops a lengthwise median ridge on the under side. 
The spinous processes maintain their laminar character throughout; they 
increase both in length and height to the middle of the series, then decrease 
in length, but continue to increase in height throughout the series; the 
anterior ones are perpendicular, as on the last dorsals; there is a gradually 
increasing backward obliquity to the end of the series. The zygapophyses, 
both pre- and post-, rise higher and higher with successive lumbars. The 
last lumbar is entirely embraced between the anteriorly projecting ilia. 
The sacrum consists of five vertebree, perfectly anchylosed, yet retaining 
evident traces of its composition. The two anterior vertebrae are much 
larger than the other three, which abruptly decrease in size. The former 
alone join the ilia; their lateral elements are completely fused with each 
other and with the centra, forming an indistinguishable mass, the outer 
roughened surface of which constitutes the sacro-iliac synchondrosis. Their 
spinous processes are, however, distinct from each other, and from those of 
the smaller succeeding vertebrae; the spines of which latter are, on the other 
hand, fused into a continuous ridge, as is also the case with their lateral pro- 
cesses. There are five pairs of intervertebral foramina on the face of the 
sacrum, the anterior pair much the largest, the posterior lying between the 
last sacral and first caudal; the corresponding apertures upon the convexity 
“of the sacrum are less conspicuous, though still discernible. The osseous 
ridge denoting the line of fused zygapophyses is plainly traceable ; the pre- 
zy gapophysis of the first sacral bears a distinct facet, for moyable articulation 
with the last lumbar. The sacrum is less than one and a half inches long, evén 
measuring the produced pre-zygapophyses, and therefore much shorter than 
the ilia, which project far in front of it; it ends opposite the posterior margin 
