PROFESSOR OWEN ON THE GENUS DINORNIS. 359 



condyloid canal {},), extends forwards and inwards through the pneumatic diploii at the 

 base of the basisphenoid, until it gets below the ' sella/ when it bends upwards and in- 

 wards to terminate at the bottom of the deep but contracted pit, close by the orifice of 

 the opposite canal, at the back part of the sella : the posterior boundary of that pit is 

 continuous with that which bounds anteriorly the part of the presphenoid that supported 

 the chiasma nervorum opticorum, at the sides of which are the large optic foramina (op, 

 fig. 3). The olfactory foramen is single and distinct on each side (is, fig. 5). 



On comparing the cranial part of the present skull with that described and figured in 

 my second Memoir on the Dinorn{s\ and assigned to D. struthoUes, there is, besides 

 the difl^erence of size, much difference in the proportions and configuration of certain 

 parts. The preservation of a portion of the smooth external inferior surface of the 

 basisphenoid in the larger cranium demonstrates that that bone did not descend half so 

 tar below the occipital condyle as it does in the present cranium of the smaller species 

 which for convenience of reference I shall assign to the Dinornis casuarinus, with which 

 It seems to agree in size. The distance from the occipital condyle to the back-part of 

 the ' sella,' where the carotid canals terminate, is the same in both ; but the canals com- 

 mence, in the strutho-ides, by orifices quite distinct from the precondyloid foramina 

 which are on the same transverse plane as the condyle itself in the larger cranium ■ 

 this IS also broader and more depressed, and the tuberosities dividing the median from 

 the lateral festoons of the supraoccipital crest are much nearer the middle line (pi. 38. 

 fig. I , r r). The outer articular cavity on the under surface of the mastoid for the tym- 

 panic is relatively much larger in the struthoUes: the temporal fossa is deeper, and is 

 separated from the occipital fossa by a wider space in the struthotdes, not by' a mere 

 ridge as in D. casuarinus: the cerebral convexities are not indicated on the upper 

 surface of the frontals in the strutho-ides as they are in D. casuarinus. The olfactory 

 chambers (pi. 38. fig. 4, is) are relatively larger and extend further back in the stru- 

 thotdes : there are obvious differences in the form and proportion of the paroccipital, 

 mastoid, and postfrontal processes, but as these are more or less mutilated in the cra- 

 nium assigned to D. struthotdes, I forbear to dwell on them in the present comparison, 

 the specific distinction being clearly established by the more important difl:erences 

 above-mentioned. 



If we next compare with the skull of Dinornis casuarinus the smaller cranium referred 

 to Palapteryx dromiotdes'-, we shall find in that specimen proof of the absence of the 

 thick and broad inferior paroccipital ridge ; the precondyloid foramina are raised to the 

 level of the condyle, and are distinct from the carotid foramina. The longest diameter of 

 the foramen ovale is transverse, not vertical as in Dinornis casuarinus. The antero- 

 posterior extent of the temporal fossa is absolutely greater in the smaller cranium of Pal. 

 dromiotdes. There is no groove in the line of the coronal suture, but a sUght trans- 



' Zoological Transactions, vol. iii. p. 308. pi. 38. figs. J -4. 

 « Tom. cit. p. 311. pi. 39. figs. 4, 5 & 6. 



