PHTLOGENY OF THE PALiEOGNATlLE AND NEOGNATH^E. 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 Dromasus. 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 Dromasus, have been regarded as more closely 

 allied to Dinornis and Apteryx than any other forms. Apteryx we regard as quite 

 distinct. The interrelationships of this group are indicated in the diagram (p. 265). 



The skeleton of Dromasus 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 Dromasus are badly needed ; as also is the adult 

 skeleton of Rhea darwini. It is interesting to note that the characteristic feathered 

 tarso-metatarsus of R. darwini is temporarily reproduced in the embryo of R. americana 

 (fig. 2 d, 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 lacking 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 n. 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 Dromceus. 



Key to the Osteology of the Pal^eognath.e, 

 based on the Characters of the Adult Skeleton. 



A. Skull. (Plates XLII.-XLIV.) 



The pterygoid free anteriorly or resting on the paired posterior ends of a large vomer; 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 length, never probe-shaped. 



a. Vomer deeply cleft posteriorly into widely expanded right and left limbs 

 running directly backwards beneath the pterygoids ; palatine articulating 



