OSTEOLOGY OF THE DODO. (57 



the angles. In the great breadth of the occipital surface compared with its depth, in 

 its flatness from side to side, and its aspect backward and a little upward, Didus most 

 resembles Dinornis. The basioccipital curves downward, and unites with the basi- 

 sphenoid in developing the pair of larger tuberosities (PI. XXIII. fig. 1, 5), which ter- 

 minate about ^ an inch below the occipital condyle. There is nothing of this structure 

 in the Columbine cranium. In one of my Dodo's skulls there is a pair of small 

 tubercles between the larger basioccipital ones ; these are not developed in the other 

 cranium. The basisphenoid is subquadrate, and flattish below, impressed by a shallow 

 median longitudinal channel. 



The hypoglossal nerve escapes by two small foramina on each side of the base of the 

 condyle ; external to these is the vagal foramen ; still more external is the depression 

 (ib. a) perforated below by the entocarotid, glossopharyngeal, and sympathetic, above 

 by the tympanic vein. The entocarotid canal opens into the hind part of the sella or 

 pituitary fossa : the vagal canal begins within the skull, above the hypoglossal foramina. 

 The paroccipital carries the posterior surface of the skull downward and outward to a 

 much greater degree than in any Dove, but to a less degree than in Dinornis. The 

 Eustachian tubes impress the outer and fore part of the basisphenoid. 



The temporal fossae (PI. XV.), in the present specimens, show the same contraction in 

 proportion to their depth by which the original skull of the Dodo, compared with that 

 of the Dinornis, ' Proc. Zool. Soc' (1848, p. 3), differed from the larger extinct wingless 

 bird. In the approximation of the postorbital process to the mastoid, Bidunculus shows a 

 closer resemblance to Bidus than does Goura, in which the temporal fossa, besides being 

 narrow, is shallow. The temporal muscle appears to spread its origin above the fossa 

 upon the sides of the cranium, forward half an inch in advance of the postfrontal 

 process, and backward to the outer angle of the superoccipital ridge. 



The parietal region is broad, flat, and short, as in Dinornis, not convex as in Doves ; 

 it is also impressed at its middle part by a shallow transverse groove, continued out- 

 ward and forward of less depth and definition, so as to mark off the convex interorbital 

 part of the swollen frontals. 



The outer side of the mastoid is convex, smooth, overhanging the tympanic ca\ity, 

 and sending off a short process, the base of which is defined in one cranium by a trans- 

 verse ridge in front of the anterior articular cup for the tympanic bone. A similar 

 process is developed in Diduncidus, not in Goura, where it is barely indicated. 



The presphenoid is compressed, but thickened and rounded below, where the pala- 

 tines and pterygoids at their junction with each other abut against it: the pterygoid 

 sends off a short process from the middle of its hinder border ; but this is not met by 

 a corresponding " pterygoid process " of the basisphenoid as in Didunculus. 



The frontals are broad and convex, rising abruptly (as in Diduncidus) above the 

 coalesced cranial ends of the nasals and premaxillary (PI. XV.) ; in Didus the breadth 

 greatly exceeds the length of the interorbital frontal convexity, as compared with 



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