PHYLOGENY OF THE PALHZOGNATHZ AND NEOGNATHA. 267 
improbable that their source may be traced to that stock which gave rise to the Rheo- 
Dinornithine type of palate and pelvis. 
Casuarius, which forms the nucleus of this research, is here regarded as only 
generically distinct from Dromeus. These two forms are, it is here contended, closely 
allied. Struthio is perhaps derived from the same ancestral stock. Hitherto, how- 
ever, these two forms, Casuarius and Dromeus, have been regarded as more closely 
allied to Dinornis and Apteryx than any other forms. Apterya we regard as quite 
distinct. The interrelationships of this group are indicated in the diagram (p. 265). 
The skeleton of Dromeus ater, procured at the last moment, at great trouble, by 
Mr. Rothschild, has proved of considerable interest in one or two respects. It does 
not differ much, however, from that of the larger species: wherein it differs it appears 
to approach the Cassowaries. I have seen no authenticated skeleton of D. irroratus. 
Skulls of adult Casuarius and Dromeus are badly needed; as also is the adult 
skeleton of Rhea darwini. It is interesting to note that the characteristic feathered 
tarso-metatarsus of &. darwin? is temporarily reproduced in the embryo of R. americana 
(fig. 2D, p. 155). 
Whether the four species of Ostrich indicated in this paper will be further confirmed 
is a point which time alone will show. It seems probable. 
I hope to be able to supply much that is Jacking in this paper by a further contri- 
bution at no distant date in the shape of an Appendix. Since this was written the 
British Museum has acquired a hind-limb of Genyornis. This is remarkable chiefly on 
account of the fact that digit 1. was becoming absorbed. The proximal phalanx was 
of great length and slenderness. In this we may trace the early stage in the evolution 
of a second two-toed Struthious bird. As Messrs. Stirling and Zeitz have shown, 
Genyornis was undoubtedly a near ally of Dromeus. 
Key To THE OSTEOLOGY OF THE PALHOGNATHA, 
based on the Characters of the Adult Skeleton. 
A. Skuut. (Plates XLIL-XLIV.) 
The pterygoid free anteriorly or resting on the paired posterior ends of a large voimer ; connected 
with the palatine either by the opposition of its outer border with the mesial border of the palatine 
or by squamous suture, or by complete fusion, but never by means of opposed glenoid surfaces. 
The vomer is always present, and paired, and is either fused with or tightly wedged in between 
the maxillo-palatine processes ; basipterygoid processes always present, of great size, seated at 
the base of the parasphenoidal rostrum, and articulating with the extreme proximal end of the 
pterygoid; nasal processes of the premaxilla unpaired ; parasphenoidal rostrum and mesethmoid 
continued forward beyond the level of the lachrymal. 
A. Beak short or of medium Jength, never probe-shaped. 
a. Vomer deeply cleft posteriorly into widely expanded right and left limbs 
running directly backwards beneath the pterygoids ; palatine articulating 
