CLASSIFICATION, AND PHYLO&ENY OF THE DINOENITHIDJi:. S99 



region. Struthio is peculiar in having a forvvardly-directed process, given off from the 

 supraorbital ridge, which meets the lacrymal, enclosing a notch or foramen. 



The nasals of the Dinornithidee differ from those of all the other Ratitse in the 

 junction with one another of their posterior ends above the ethmoid, so that none of 

 the latter appears on the surface. In the Ostrich, Rhea, Emu, and Kiwi a lozenge- 

 shaped area of the ethmoid appears between the bases of the nasals ; in the Cassowary 

 the same arrangement obtains in the young birds (25) at the time of hatching, but in 

 the adult the actual condition of things is hidden by the development of the crest. 



The maxillary process of the nasal is well developed in Struthio and Apteryx, 

 extremely small and delicate in Dromceus, absent in S/iea and C?) Casuarius. It is 

 somewhat remarkable that the absence or vestigial nature of this process should be 

 given as a general character of the Eatitse by Garrod (4) and Fiirbringer (3). 



On the base of the skull of the other Ratitse the basitemporal platform is not raised 

 beyond the general level of the skull-floor to anything like the same extent as in the 

 Moas, and the precondylar fossa is therefore comparatively shallow. It is best defined 

 in Apteryx, in which also the mamillar processes are even longer proportionally than in 

 the Dinornithidee, while in the other genera they are considerably less developed, 

 being fairly prominent in Casuarius, small in Dromceus and Struthio, and obsolete in 

 Mhea. 



The paroccipital notch may or may not be bridged over by bone. The vagus foramen 

 lies in the notch in Apteryx^ Dromceus, and Casuarius, mesiad of it — as in the Moas — 

 in Struthio and Ilhea. In the Australian genera the ventral edges of the Eustachian 

 tubes are prominent and sometimes meet, converting the groove into a canal. In the 

 Ostrich, Rhea, and Kiwi there are actual tubes, the closure of the groove being more 

 complete in the two first-named genera than in Apteryx. 



Another variable point is the extent to which the carotid canal is closed by bone 

 and the resulting position of its external aperture. In the Ostrich, as in the Moa, the 

 carotid foramen lies in or slightly in front of the paroccipital notch ; in the Emu and 

 Cassowary it is on the lateral surface of the basitemporal platform, immediately caudad 

 of the Eustachian groove and laterad of the mamillar tuberosity ; in Rhea it is in a 

 similar position, but slightly further forward ; and in Apteryx it is altogether in front 

 of the mamillar tuberosity and fully visible from below. 



The basipterygoid processes are most dinornithic in Apteryx and Dromceus ; in the 

 other three genera they are proportionately longer and more slender. Between their 

 bases the minute anterior basicranial fontanelle sometimes occurs in Struthio, Rhea, 

 Casuarius, and Dromceus, but I have never seen any trace of it in the adult Apteryx. 

 Amongst my specimens a young Rhea is the only one showing any sign of the posterior 

 basicranial fontanelle. 



The rostrum of the Ostrich is rounded below ; that of all the other genera is keeled, 

 except at the posterior end, tlie carination being most marked in Apteryx. 



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