PROFESSOR OWEN ON THE GENUS DINORNIS. 363 
The beak is more elongate, more decurved, more depressed terminally; the outer 
wall of the premaxillary extends so far back, before the divergence of the maxillary and 
nasal branches, as to hide from view the prenarial septum and convert the cavity on 
each side into a fossa. This septum is exposed in Dinornis'; and a shallow depression 
on each side represents the cul-de-sac of Aptornis. 
The nasal branch of the premaxillary coalesces with the frontals and nasals. The 
- maxillary branch of the nasal is longer, and directed more forward, leaving a larger 
antorbital vacuity (Pl. XL. fig. 1, v) in Aptornis. In Dinornis, as in Apteryx, the 
maxillary branch of the nasal descends anterior to and in connexion with the lacrymal’, 
leaving no antorbital vacuity distinct from the external nostril. The mandible, besides 
the difference in shape and articulation, has the angle deflected. 
It is instructive to find in the cranial organization of Aptornis these evidences of 
family distinction from Dinornis repeated in the second species of the genus, although 
the fact was more plainly and decisively shown by the leg-bones in the Memoir 
(Part III.) of 1848". 
In the downward production of the basilar platform Aptornis differs from Notornis 
more than it does from Linornis; it differs from Notornis and all Coots (Rallide) in the 
development of the premastoid process and its junction with the postfrontal; from the 
same group it differs in the adze-like form of the bill, which is commonly in Coots, as 
in Notornis, not only pointed but straight; Aptornis further differs in the entire, imper- 
forate structure of the mandibular ramus, and more especially in the absence of the 
outer narrow second synovial articular surface for the tympanic. When to these well- 
marked differences we add the form and proportions of the metatarsus of Aptornis*, the 
ornithologist might be pardoned for pausing before referring the present remarkable 
genus to the Rallide. 
In Aptornis, e. g., the metatarsus is but three-fifths the length of the femur; but it is 
quite as broad as that bone at the middle of the shaft, and both articular ends expand 
to corresponding proportional dimensions. 
The two upper articular surfaces of the metatarsus are very nearly on the same level, 
the inner one being rather the higher; and the intermediate eminence is broad and 
high. The calcaneal process is abruptly prominent, and is perforated, the outer and 
inner crests having coossified around the flexor tendons; such structure has not been 
seen in any Coot. ‘The outer and inner calcaneal crests are distinct in Rallidw—the 
outer one being most produced, but subsiding more gradually to the level of the shaft 
of the metatarsus than in Aptornis. 
Yet the following correspondences of cranial structure show, unequivocally, a closer 
‘ Trans. Zool. Soe. vol. vii. pl. 10. fig. 1, s. 
? Tb. vol. y. pl. 55. fig. 1, 15"; vol. ii. pl. 54. In this specimen the suture between the nasal process and the 
lacrymal was obliterated, and both were referred to the lacrymal (ib. 286). 
* Trans. Zool. Soc. vol. iii. p. 346. ‘ Tb, vol. iy. pl. 3. figs. 5, 6, 7, 8. 
3D 2 
