PROFESSOR OWEN ON THE GENUS DINORNIS. 145 
skull I now believe to have belonged to the Dinornis otidiformis of the first Memoir 
(1843), vol. iii. p. 247, pls. 25, 26. fig. 5, founded on a tibia, but recognized by the sub- 
sequent acquisition of the metatarsal as a distinct genus, Aptornis, belonging to a 
distinct family, perhaps order, of birds from that to which Dinornis belongs. The 
rectification was made in my fourth and fifth Memoirs (1850), vol. iv. Trans. Zool. Soc. 
pp. 10 and 62. Upon that rectification J lost the best ground on which I had pre- 
viously based the generic distinction of Dinornis from Palapteryx; and now there 
remain the degree of development of the abortive and functionless back toe, which I ° 
cannot regard of generic importance, and the proportions of sternum, limb-bones, and 
rostral part of the beak-bones, all more or less gradational. With the breadth of trunk 
concomitant with limbs so robust and divergent as in D. robustus, D. elephantopus, and 
D. crassus, the sternum is broad in proportion to its length, and the side processes more 
divergent’; yet the dinornithic type of that bone is closely kept. 
The robuster-limbed and broader-bodied Moas, however, do not all show the short, 
broad, obtuse form of beak; and I confess that the general conformity of cranial struc- 
ture under the modifications illustrated in the present Memoir do not promise an 
advantage, by drawing a line which must be more or less arbitrary in whatever direc- 
tion, equivalent to the imposition of two names for such divisions of a group of species 
so natural and closely allied as T would at present indicate by the sole generic name 
Dinornis. 
On the Cranium of a Gigantic Bird (Dasornis* londinensis, Ow.) from the 
London Clay of Sheppey, Kent. (Plate XVI.) 
The study and foregoing illustrations of the cranial structure of the recently extinct 
species of large terrestrial birds, induce me no longer to defer communicating similar 
evidence of one which passed away at a much more remote period of geological time. 
This evidence is the cranial part of the skull, which has been reduced by rough usage of 
the elements to a similar state with that of the cranium of Dinornis giganteus above 
described (p. 138). Very little of the outer table of the walls of that cavity is preserved ; 
and much of the thick pneumatic diploé is exposed, not only along the upper (parieto- 
frontal) walls, but at the back and base of the cranium. 
To this state it appears to have been brought, probably in its transport seaward by 
the mighty eocene river, prior to petrifaction in the mud with which it finally became 
enveloped. In the mass of such matrix, converted into petrified “ London clay,” of 
which geological formation the Isle of Sheppey now mainly consists, this cranium was 
gathered with other eocene fossils, and was obtained from a local collector by the 
Earl of Enniskillen, F.R.S., to whom I am indebted for the opportunity of describing 
1 Memoir XIII, vol. vii. Trans. Zool. Soc. 
* Sdoos, a thicket (in reference to the abundance of fossil fruits and other arboreal evidences associated with 
the remains of the large bird). 
