89 
of Dinornis didiformis, characterized by superiority of size, or to a distinct species of 
Dinornis. 
Comparing the femora f 6, f13 (Pl. XXIII. fig. 1.) and f16 (Jb. fig. 2.) with each 
other, it was obvious that one of them differed in its proportions from the rest, f 13 being 
relatively thicker, as is shown in the plate and in the table of admeasurements. This 
femur corresponded much more closely with the femur f 12 (Pl. XXI. fig. 3.) in its general 
form, its ridges and tuberosities ; but these were less strongly developed, and the manner 
and extent of abrasion of both proximal and distal articular surfaces would well accord 
with the supposition of their having been in that cartilaginous or less completely ossified 
state which characterizes the femur of a bird not quite fully arrived at maturity. The 
state of development of the muscular ridges and tuberosities forbids the reference of 
this femur to a very young bird, but supports the conclusion that the bone had belonged 
to an individual as far advanced in growth as is indicated by the difference in size be- 
tween it and the femur f 12. 
The different condition and proportions of the two remaining femora, of 93 inches in 
length, f 6 and f 16, establish their specific distinctions from the femora f 13, f 12 and 
f2. Of this I think no doubt can be entertained by any anatomical naturalist who 
may inspect the plate (Pl. XXIII.) containing the figures of f 13 and f 16, selected for 
the comparison, or who may give due consideration to the following statement of their 
differential characters. 
These bones are of equal length but of unequal thickness: the shape of the shaft of 
the bone is also different ; the relative antero-posterior diameter of f 13 is much greater 
than that of f 16, especially at the proximal end and trochanterial enlargement of the 
shaft, and just above the inner condyle: the anterior surface of the proximal part of 
the shaft presents a shallow equable concavity in f 16 which is not present inf 13. In 
f 16 a pretty sharp ridge leads from the middle of the posterior surface of the shaft ob- 
liquely to the upper and posterior angle of the inner condyle, and the posterior surface 
of the expanded shaft above the condyles is regularly excavated by a moderate concavity 
which is continued uninterruptedly into the inter-condyloid depression. In f 13 an 
oblong rough tuberosity, with its long axis parallel with that of the bone, exists in the 
place where we find the oblique ridge in the other bone, the tuberosity being separated 
from the upper and posterior angle of the inner condyle by a smooth channel or de- 
pression, which leads to an oval depression much deeper and more circumscribed than 
is the corresponding concavity in f 16. The complete development of the muscular 
ridges and tuberosities, with the better preserved state of the articular extremities, show 
the femur f 16 to be a more mature bone than f 13; the differences in proportion and 
configuration prove it to belong to a distinct species from Dinornis struthoides. 
We next come to the question whether the femora f 6 and f 16 belong to the species 
Dinornis didiformis, founded on the femora f 7, f 8, f 17, the tibia ¢ 3, ¢ 4, #5, ¢ 8, t9, 
# 10, and the metatarsi m 4, m 5 and m 6, and whether the femora f 6 and f 16 
N 
