374 PROFESSOR OWEN ON THE GENUS DINORNIS. 
the anterior border is rather more sharply produced, and is brought more to the front 
surface of the bone. A linear ridge is continued therefrom down three-fourths of the 
shaft, inclining toward its inner side. A tuberosity projects below the base of the 
trochanter at the outer side of the bone, from which goes a linear ridge along the back 
part of the shaft, toward the outer side; a second linear ridge, commencing lower 
down, runs along the back of the shaft towards the inner side as far as the popliteal 
space; between these ridges, near halfway down the bone, opens the canal of the 
medullary artery. ‘The distal end is less expanded than in Aptornis or Cnemiornis. 
The rotular channel, though wide, is relatively deeper and narrower than in Aptornis, 
and the inner border is more produced. A small tuberosity projects external to the 
upper end of the outer border: this may be individual. The popliteal space shows no 
definite fossa, and its surface is irregular. The fibular articular groove is deeper, with 
a better-defined and produced outer border. As in the thigh-bone of the Rallide 
generally, there is no pneumatic foramen. 
§ 7. Metatarsus of Aptornis defossor. 
In general form and proportions this bone resembles that in Aptornis otidiformis: 
the superiority of size is shown in the “Table of Admeasurements,” and in figs. 1 & 6, 
Pl. XLIV. As compared with Dinornis (ib. figs. 7-10), the metatarsal of Aptornis 
defossor shows the same greater depth and nearer equality of size of the two condylar 
cavities (Pl. XLIV. fig. 4), with the broader and loftier intercondylar tract, as in Apt. 
otidiformis', the same superior prominence and perforation of the calcaneal process 
(ib. c,¢'), the same flattening of the back part of the shaft through the non-projection 
there of the upper half of the mid metatarsal element, also the presence of the canal 
(ib. ¢) for the tendon of the “ adductor digiti externi.” The inner (entotibial) condylar 
cavity is on a rather higher level than the outer (ectotibial) one, is rather deeper, 
rather less from before backward. ‘The cavity at the upper part of the front surface 
of the metatarsal shaft is relatively less deep than in Aptornis otidiformis; it is not con- 
tinued so low down upon the shaft; but the anterior outlets of the interosseous canals 
open separately at its bottom, and the ridge at the inner border for the insertion of the 
corresponding part of the tendon of the “ tibialis anticus ” is strongly marked and defined. 
In Dinornis the interosseous canals converge from behind forward to a common orifice 
(0, fig. 7) at the bottom of the shallow upper and anterior depression. In one specimen 
of metatarsus of Aptornis defossor the groove (f, fig. 1) for the tendon of the “ adductor 
digiti externi” deepens as it approaches the interspace between the middle and outer 
digital trochlex, and perforates the bone above that interspace; in another it deeply 
grooves the interspace, but is not crossed by the bony bridge at the fore part of the 
interspace. A similar variety is shown by one of three specimens of metatarsus in Apt. 
otidiformis. Where the bridge exists, the tendinal canal opens in the interval or chink 
1 Trans. Zool. Soc. vol. iv. p. 11. 
