AXIAL SKELETON OF THE OSTRICH. 439 
There is a small pneumatic foramen in the vertebral margin near the head of the rib. 
The dorsal (or more postaxial) margin of the rib is rather shorter than the ventral 
one, owing to the head and neck being slightly longer than the tubercle. 
THE VERTEBRAL RIBS OF RIGHT SIDE (size of figures I-X, } natural size; figures IV’, V’, VII’, 
3 natural size). 
Fig. 75. 
1. first rib: its preaxial margin is between / and ¢; its vertebral margin extends downwards from ¢ to the apex 
of its ventral margin. II. second rib. III. third rib, IV, fourth rib; IV’. proximal end of fourth rib, 
. showing the pneumatic foramem (f), the cup-like surface for the diapophysis (¢), and the convex tubercle 
(h) for the parapophysis. VY. fifth rib; V’. its proximal end (the small but sharp prominence near the 
letter f is produced by the ridge which passes outside the root of the capitulum), VI. sixth rib. VII. 
seventh rib; VII’. its proximal end, showing the great articular surface for the diapophysis and 
the very large pneumatic foramen. VIII. eighth rib, showing the small opening or defect of ossification 
on the tuberculum, near its junction with the capitulum. IX. ninth rib, showing a defect of ossification 
larger than that in the eighth rib. X. tenth rib, with a defect of ossification relatively yet larger. In all 
the figures, 2 denotes the capitulum, and ¢ the tuberculum ; w, the uncinate process. 
The Second Rib. : 
This still absolutely small rib (fig. 75, 11) is relatively much elongated compared with 
the first rib, its length being about three times its greatest breadth, and three times the 
