PROFESSOR OWEN ON THE GENUS DINORNIS. 37 
oa 
the sides of the perforate calcaneal process in Aptornis. If the ento- and ectocalcaneal 
plates of Notornis' or of Porphyrio were united by coossification of their free borders, 
the condition of the calcaneal process in Aptornis would be produced. One can see the 
advantage of a complete bony pulley for the traversing tendon of the flexors of the 
toes”; and this was a strong one in Aptornis, with a pulley to match. The base of the 
perforated process equals half the transverse diameter of the proximal end of the meta- 
tarsus, outstanding a little to the outer side of the middle of the hind part of that 
surface, slightly deflected at the end. The inner wall has a longer base of origin than 
the outer one. There is a feeble indication of the parts of the canal respectively 
traversed by the “ perforans” and “ perforatus” tendons, but no outside grooves; and 
the difference from the gallinaceous metatarsus is shown by the non-continuation of the 
entocalcaneal plate with the postinternal crest on the shaft of the bone, giving attach- 
ment to one of the divisions of the sheath-forming insertional tendon of the “ gastro- 
chemius externus”*. 
The beginning of the postinternal crest is separated from the entocalcaneal process 
by a canal about 1} line wide, into which opens the antero-posterior (interosseous) 
canal between the inner and middle metatarsal elements. ‘The surface on the inner 
side of the postinternal crest for the origin of the “ flexor brevis pollicis” is extensive 
and well marked, according with the size of the digit indicated by the hallucial articular 
surface (Pl. XLIV. fig. 5,1). The anterior surface of the metatarsus is impressed, near 
the tibial articulation, with a deep fossa, into which open the two “ interosseous ” tubular 
canals; beneath these are surfaces for the origins of the ‘ extensor pollicis brevis” and 
“adductor digiti externi;” and the inner side of the fossa is produced into a short ridge, 
into which the tendon of the “ tibialis anticus”* is in part inserted. Midway down the 
fore part of the shaft begins the groove for the “ adductor digiti externi,” the tendon of 
which glides through the canal above the interval between the middle and outer trochlear 
condyles, which canal is present in the Notornis and Coots, though by no means peculiar 
to them. It is one of the well-marked distinctions between the metatarsus of Aptornis 
and of Apterya, this latter bird agreeing with Dinornis in the absence of the intertro- 
chlear canal. 
The surface below the postinternal crest indicates a strong and large back toe (hallux, 
Trans. Zool. Soc. vol. iv. pl. 3. fig. 5, 1); but Motornis and the Coots have this in common 
with the Rasores. The trochlee of the digits 11 & 1v descend almost to the same level ; 
Iv is, perhaps, rather the lowest ; in Notornis and the Coots it is more decidedly so. The 
mid condyle is more advanced and more produced in Aptornis, as is usual in Gralle and 
Galline, and as it is, indeed, in Apteryr and Dinornis. The interval between the toes 
* Trans, Zool. Soe. vol. iv. pl. 2. fig. 3. 
? Trans. Zool. Soc. vol. iii. “ Myology of Apterya,” pls. 22, 25, 1, 3, 4, 5, 6. 
* Op. cit. vol. iii. pl. 85, R*¥**, * Ib. ib. 8. 
VOL, VII.—PART v. January, 1871. 3F 
