56 PROFESSOR OWEN ON THE 
postzygapophyses (z'), converging towards the middle of the upper surface of the neural 
arch, being arrested, save in one instance, at the sides of the ligamentous surface 
occupying the common position of the base of the neural spine. 
In the axis vertebra (Pl. XVII. figs. 12 & 13) the posterior articular surface, concave 
vertically, and 3 lines in that extent at its middle part, is very convex transversely, being 
continued upon the sides of the posterior part of the centrum; a thick obtuse hyp- 
apophysis (fig. 13, hy) descends below this surface: the anterior or odontoid surface 
presents the usual form in birds; the odontoid process (ib. z) has a pit at its apex. 
The prezygapophyses (fig. 12, z), of very small size, project from the outer and fore 
border of the neural arch, with their articular surface looking outward and slightly 
upward; a ridge is continued from their back part to the base of the postzygapo- 
physes: the surface (fig. 13, z') in these, 43 lines in long diameter, is three times the 
size of the anterior one; it is concave transversely, and looks downward and a little out- 
ward. The anapophyses (ib. fig. 12, @) are large tubercles rising above the articular 
surfaces. The base of the neural spine, 9 lines in length (ib. ms), is coextensive with 
the neural arch; the spine rises posteriorly to a height of 6 lines, with a thickness of 2 
lines, having a convex upper margin (Pl. XV.). 
The relative size and position of the cervical vertebra, as coadjusted in the position 
and degree of flexure of the neck represented in Sir Hans Sloane's life-size painting of 
the Dodo, in the British Museum, are given in Plate XV. with the varying proportions 
of the pleurapophyses and other processes. 
§ 3. Rids. (Plates XV. & XVI.) 
The specimens of ribs include both vertebral and sternal portions; that which appears 
to be the second or third on the right side (Pl. XVI. figs. 7, 7 @) is 4 inches 4 lines 
in length (following the outer curve), and expands to a breadth of 7 lines at its lower 
part; the interval between the articular surfaces of the head and tubercle is 6 lines. 
The appendage (ib. a) has coalesced with the middle of the hind margin of the shaft. 
The neck is compressed, with a thin upper margin; the lower one is continued with 
a curve upon a strong internal buttress-like ridge (ib. 6), which runs to near the fore 
part of the flattened body of the rib, where it meets the ridge continued from the 
tubercle, about 2 inches down the rib: there is a shallow channel between these 
ridges, contracting to their confluence. The inner surface of the rib is impressed by 
a deeper and broader channel behind the buttress: the posterior border expands in 
in the form of a triangular plate, with a base of about an inch in extent, due to the 
complete confluence there of the epipleural process. ‘The anterior border is thicker, 
and isalmost straight. Towards the sternal end the pleurapophysis contracts and thickens, 
terminating in a rough syndesmotic elliptical surface, 3 lines by 2 (fig. 7,/), for the at- 
tachment of the hemapophysis or sternal rib. 
A vertebral rib (ib, fig. 2) which is entire, measures 9 inches in Jength (following the 
