PHYLOGENT OF THE PAL^OGNATH^ AND NEOGNATHJE. 173 



in the form of this platform. In Dromceus ater it is very sharply defined, presenting 

 a steep face to the pre-condylar fossa ; in the other species of Dromceus and in Struthio 

 this face slopes gently upwards and backwards. Thus, in all save D. ater, the pre- 

 condylar fossa is shallow and moderately wide. 



The pre-temporal platform is very sharply defined in Avteryx, Dinornithidce, and Rhea. 



In Apteryoc and Dinornithince amongst the Moas, it is roughly triangular in form, 

 its postero-lateral angles are produced downwards into moderately or very large 

 mammillary processes. These in some of the Dinornithince coalesce in the middle 

 line, and present a deep vertical face when the skull is seen from behind. In the 

 Emeince the platform takes a laterally expanded pentagonal form, sharply defined along 

 its antero-lateral angles by a raised ridge helping to form the Eustachian groove. 

 The anterior basicranial fontanelle is marked by a deep groove. In Mpyomis the 

 basitemporal platform is much shortened antero-posteriorly. The mammillary tubero- 

 sities run in the form of a low rough ridge along the whole of each postero-lateral side 

 of the pentagon. 



In Shea the platform has the shape of an elongated pentagon presenting steep 

 faces on all sides, though anteriorly it may slope gradually into the rostrum. The 

 Eustachian apertures lie immediately below the bases of the basipterygoid processes. 



The Eustachian grooves are short, widely separated one from the other in the middle 

 line, and, in all except Dinornis and Casuarius, arched over by bone. In these last the 

 groove remains permanently open. In Rhea, Struthio, and Dromceus the mouth of the 

 aperture of each is conspicuous, lying on either side of the base of the basipterygoid 

 processes. In Apteryx they lie nearer the middle line and are inconspicuous. In the 

 Tinamous these apertures are very wide apart, opening immediately behind the basi- 

 pterygoid processes. 



The paroccipital notch is more or less wide in all save Apteryx, where it is narrow 

 and deep. As in Rhea, it is more or less completely bounded on its outer side by a 

 much compressed, forwardly directed lamina of bone from the paroccipital process 

 (p. 172). 



Within this notch, in Struthio, Rhea, Dromceus, Casuarius, Apteryx, and the Tinamous, 

 occurs the vagus foramen for the ninth and tenth nerves, the condyloid foramina for 

 the exit of the twelfth nerve lie behind it, between it and the occipital condyle. 



In the Dinornithince the vagus foramen occurs behind the notch and much nearer to 

 the condyloid foramina, forming, with them, a little cluster of apertures, that of tne vagus 

 being much the longest of the group. The carotid foramen in the Dinornithidce lies 

 immediately in front of the notch, in all the other forms it occurs some distance further 

 forwards. 



Traces of both anterior and posterior basicranial fontanelles occur in many of these 

 Palaeognathine skulls, sometimes both are indicated in the same skull. The former 

 is the small pit in the middle line between the anterior ends of the basipterygoid 



vol. xv. — part v. No. 9. — December, 1900. 2 c 



