456 DR. J. MURIE ON SAIGA TARTARICA. [June 9, 
The caudal vertebree may conveniently be regarded as consist- 
ing of two kinds :—those exhibiting enlarged or moderate-sized, 
and those with very diminished or obsolete processes. Of each 
there are five or six, according to where the line of demarcation is 
fixed ; for the gradation of change is the opposite of abrupt. The 
three proximal to the sacrum distinguish themselves by the length 
of the neural spine, which runs backwards as a narrow, depressed, 
triangular bar, almost touching the root of the spine posterior to it. 
The third is rather shorter. The neurapophyses are well developed 
in each. In the first the transverse process is broad, assimilating 
to the hinder end of the sacrum. In the succeeding two the trans- 
verse processes are smaller and slant outwards and backwards from 
the distal segments of the body. The fourth, fifth, and sixth ver- 
tebree have altogether much shorter processes, dorsal and lateral. 
The remaining caudal bodies are more or less expanded at each 
extremity. The tail as a whole is feeble, and terminally slender. 
(B) Costal Arches and Sternum.—Of the thirteen vertebral * 
ribs the anterior eight have sternal attachments, the remainder come 
under the heading of floating or free ribs. The front five are more 
or less vertically placed, the sixth and those posterior by degrees take 
a wider sweep backwards. To the eighth, counting from before 
backwards, they progressively increase in length; thence they di- 
minish in quicker ratio to the thirteenth. The last and the third 
ribs are subequal in length, the first and the second the shortest. 
The first costal arch, including its presternal keystone, when exa- 
mined in front or from the interior of the thorax, is short and nar- 
row; the remainder of the costal cavity by degrees enlarges, and is 
absolutely wide at the last ribs. 
The first rib, stoutish and with little of a curve, is 43 inches in 
its chord of diameter. It is flat, as are all the ribs within, but it is 
the most convex exterually. Its angle and capitulum are thick ; and 
the sternal end (vide fig. 3) is also much elongated. 
These characters are considerably reduced in the 2nd and 3rd. 
The 4th, 5th, 6th, and 7th are remarkably thin, and broaden out 
distally. The 8th and ribs posterior are much narrower. The 
angles in all the ribs are badly defined. 
The first sternal rib (Parker), or costal cartilage, abuts against the 
uppermost presternum, and is very short. The succeeding four 
sternal ribs are each about | inch long; the 6th, 7th, and 8th 
lengthen and strengthen considerably, the rest of the free cartilages 
(sternal ribs) are wider, but long and styliform. 
Seven osseous segments can be traced in the adult sternum (fig. 
3); the last three, however, are adnate and interossified, those in 
advance have a meagre cartilaginous separation. The preesternum 
(p.st.), thick and narrow, is set at an obtuse angle upwards to the 
other sternal elements. Viewed ventrally, the 1st mesosternal piece 
(m.st.) has a cup-shaped outline, the narrow end forwards; the 
* In using the term “vertebral,” in contradistinction to “sternal” rib, I 
follow the precise morphological nomenclature of my friend Mr. K. Parker, in 
his valuable monograph ‘Shoulder-girdle and Sternum’ (1868). 
