1870. ] ANATOMY OF THE PRONGBUCK. 367 
spinal muscular fossee deep. Between the last lumbar and first 
sacral vertebral lamina there is a large lozenge-figured interspace. 
The funnel-shaped sacrum has a length of 31 inches; and its 
anterior transverse diameter is almost as much. The sacro-iliac syn- 
chondrosis is formed by a single articulation of the foremost verte- 
bral element; it possesses but a diminutive neural process. The 
three hinder vertebrze belonging to the sacrum are partly anchylosed, 
and possess spines subequal in height; their transverse processes 
are anchylosed, so as to form a tapering vertical plate of bone par- 
allel with and as high as the neural spines. 
The caudal vertebrae, as already mentioned, were imperfect, five 
alone being present, the small terminal factors having been lost. 
Those extant, together 44 inches in length, were remarkably porous, 
evincing a diseased condition or atrophy of the cancellous tissue. 
The first or anterior caudal possessed broad transverse processes of 
bony plates, but gave off no backwardly extending zygapophyses ; 
the remaining vertebral bodies diminished in size, but each had long 
slender prominent spicula passing distally. 
~mSt, 

Ventral view of the sternum and sternal ribs. 
p.st. Presternum, mm. st. Mesosternum. «. Xiphosternum. 
(6) Chest.—The eight elementary constituent parts of the sternum 
are partially coalesced, so that it appears to be composed of but five 
separate pieces. Of these the foremost are narrow, stout, and cylin- 
droid, the middle and hindmost on the contrary wider and thin. 
The manubrium or preesternum ( p. s¢) of Parker* is bifid anteriorly. 
It is a short stout bone, with an upward projecting boss between the 
first two ribs. The thick vertically narrow second and the rather 
wider third elements are ossified together; the fourth and fifth 
expand in breadth but diminish in thickness. The sixth, seventh, 
and eighth foetal segments are firmly united, the seventh or post- 
mesosternal being the broadest of the whole series. 
The xiphosternum or ensiform piece (“) is a long, flat, and strong 
process of bone, narrowing considerably at its distal and finally 
truncated extremity. 
Eight sternal ribs or costal cartilages on each side abut against 
the lateral margins of the sternum. 
The ribs number thirteen pairs, of which eight are true and five 
false. The first two are nearly straight or with but slight arching. 
* «The Shoulder-girdle and Sternum in the Vertebrata,’ Ray Soe, 1868. 
