90 
represent a sexual superiority of size, or are specifically distinct from the shorter 
femora. 
If the discrepancy of the thickness of the shaft as compared with the length of the 
bone be sufficiently obvious in femora of equal length, like f 13 and f 16 (Pl. XXIII), it 
becomes still more striking when the more robust proportions are exhibited in a femur 
of shorter size, which is one of the first differences that strike the eye in comparing f 6 
and f 16 (Pl. XXII.) with f 7, f 8 and f17 (Pl. XXIV.). The table of admeasurements 
shows that the femur f 17, which is one inch and five lines shorter than the femur f 16, has 
very nearly an equal circumference of the middle of the shaft, and a quite equal breadth 
of the distal end, the antero-posterior diameter of the condyles being also the same in 
both. If the comparison of these two femora be pursued into further details, it is seen 
that the anterior margin of the great trochanter is more produced but narrower in f 16 
than in f 17, that the anterior surface of the shaft is more convex, and that the anterior 
curve of the outer condyle is shorter in the longer femur: the antero-posterior diameter 
of the great trochanter and of the shaft, especially of that part leading to the outer 
condyle, is less in the longer femur. With regard to the configuration of the popliteal 
space, the same differences exist between f 16 and f 17 as have been already pointed 
out between f 16 and f 13, viz. a circumscribed tuberosity (d, fig. 2. Pl. XXIV.) in 
place of a continuous ridge (d, fig. 2. Pl, XXII), a deeper and smaller instead of a shal- 
lower and larger concavity, &c. 
In regard to the relation of these differences to sex, it is to be observed, that the male 
Ostrich slightly exceeds the female in size, and the difference between the two sexes of 
the Apteryx is relatively greater, yet the femora and other bones of the leg do not differ 
at all in proportions or configuration, but only in size, corresponding in degree with 
the rest of the body. I am not, indeed, aware of a single fact in the osteology of ex- 
isting birds which would justify the conclusion that the differences presented by the 
femur #16, as compared with f 17, were merely sexual. It has already been shown 
that the differences between f 16, as compared with the femora f 13 and f 12, cannot 
depend upon nonage, and, @ fortiori, the femur f 16 cannot be regarded as belonging to 
a young individual of the gigantic species: there remains then only the conclusion that 
it must represent a fifth distinct species, of which there are neither tibie nor metatarsi 
in the present collection. I venture to surmise that the tibia, and especially the tarso- 
metatarsus of this species, will be found relatively longer and more slender than in the 
Dinornithes struthoides and didiformis: so much may be anticipated from the more 
slender proportions of the femur, which, moreover, resembles the femur of the Emeu in 
some of the characters by which it differs from the above species of Dinornis, viz. in the 
sharper anterior border of the great trochanter, the more equable and deeper concavity 
between this border and the head of the femur, and in the uninterrupted ridge leading 
from the middle of the back part of the bone to the inner condyle. The generic cha- 
racters of Dinornis arc, however, manifested in the absence of the air-hole and air-cavity 
