84 
A reference to the subjoined table of admeasurements will show that ¢ 4 (Pl. XXV. 
& XXVI. fig. 3.) is thicker in proportion to its length, has relatively broader proximal 
and distal extremities, and a longer ridge for the attachment of the fibula. 
Tibia, Pi: t 2. t 7. t 4, i 3. ?8, t 9, iL 
Tx. Lin. In. Ling In. Line 3 In. Lin. $n, Lin. §$In. Lin, 3m, Lin. In. Lin. 
Length silane biases. tear 30 O 29 0 25' O 16 3 15 6 15. 4 15 4 8 6C«O99 
Breadth of proximal end.... 7 6 6 2 0 0 4 6 4 5 0 0 0 0 2 0 
Breadth of distal end ...... 4 0 ey 0 0 24 2 4 0 0 0 O lon 
Circumference of middle.... 6 6 5 3 & 4 1 4 0 0 O v0 O 1 11 
Fibular ridge extendsdown.,13 0 12 0 O 0 7 0 6 10 0 0 0 O 3 6 
The anterior ridge c at the proximal end of the bone is nearer the middle in ¢ 4 than 
in ¢ 2 (Pl. XXV. & XXVI. fig. 1.), the interspace between that and the external ridge 
being of the same breadth in both, notwithstanding the difference of total breadth. 
The external proximal ridge curves more abruptly outwards from the shaft of the bone 
in the small than in the large tibia, whereas the contrary character ought to have been 
manifested if the difference of size had depended on difference of age, such muscular 
ridges being more strongly produced in old than in young birds. The shaft of the bone 
is flatter antero-posteriorly, compared with its breadth, in the small than in the large 
tibia, and is more nearly triedral, owing to the greater flatness of the inner and anterior 
surface and the less rounding off of the inner margin, All the four tibiee of from fifteen 
to sixteen inches in length correspond in these differential characters, when compared 
with either of the two gigantic tibiz ; and the two mutilated shafts of the smaller tibiz 
equally differ in the subtriedral character from the mutilated shaft of the large tibiz. 
At the distal end of the bone, the angle formed by the posterior contour of the con- 
dyles is of a different form in ¢ 2 (Pl. XXV. fig. 2.) and ¢ 4 (Pl. XXV. fig. 4.): in the 
latter the outer condyle forms a greater proportional share of the articular surface, and 
the line of the inner one g extends more abruptly backwards. 
All the shorter tibize, as before observed, present the characters of full maturity ; the 
ridge for the fibula and those at the proximal end of the bone are quite as strongly de- 
veloped as in the tibize of double the length. 
In the tibia of a half-grown Ostrich I find the antero-external ridge, which in the 
adult projects strongly from the head of the bone, in the state of cartilage, the fibular 
ridge undeveloped, and both articular extremities in a state of epiphysis and incom- 
pletely ossified: the same conditions which influence, as has been already remarked, 
the tardy ossification in the Ostrich must have been still more operative in the Dinornis, 
in which the absence of air in the femur indicates as low a development of the respira- 
tory system as in the Apteryx. 
If this reasoning be admitted to establish the maturity of the bones ¢ 3, ¢ A EBL YD, 
it equally proves that of the tibia t 11 (Pl. XXV. & XXVI. fig. 5.), which bears the 
' According to the obvious proportions of the articular extremities when entire, 

