PROFESSOR OWEN ON THE GENUS DINORNIS. 61' 



paroccipital. The antero-posterior extent of the temporal fossa {ib. fig. 2, 7, tr, 12) is 

 one inch eight hnes, indicating, with the depth of the same fossa, the great strength 

 of the temporal muscles of this bird. The median part of the roof of the orbit is 

 slightly convex towards that cavity : the lateral part becomes concave by the remarkable 

 downward production of the postfrontal. But, perhaps, the most extraordinary features 

 are the olfactory depressions on the under surface of the frontals, the dimensions of 

 which have already been given. The great extent of these depressions has been dwelt 

 on in previous memoirs as peculiarly characterizing the great wingless birds of New 

 Zealand, and it becomes remarkably striking in the present large cranium. The olfactory 

 foramen opens into the upper part of the posterior third of these cavities, and the 

 grooves which radiate from each foramen indicate the dispersion of the branches of 

 the nerve after its emergence from the cranium. One cannot avoid the inference that 

 the living bird must have been remarkable for its acuteness of smell. The deep 

 circular ' sella turcica' has not increased in the same ratio : there is a special depression 

 at its back part above that which receives the orifices of the entocarotid canals. 



The upper and median branch of the premaxillary {ib. fig. 1, 22') slightly expands at its 

 flattened cranial end, but that part is broken away which would have filled the depression 

 on the frontal {ib. 22"). Allowing for it according to the proportions of the cranium with 

 the entire lower jaw restored at pi. 54. vol. iii., the length of this skull would be about 

 eight inches. But the skull is much shorter in proportion to its breadth than in the existing 

 large Struthious birds, or than in the Palapteryx described and figured, vol. iii. p. 361, 

 pi. 54. As the median branch of the premaxillary advances forwards, it decreases in 

 breadth and increases in thickness ; its outer margins become rounded, and it sends down 

 from the median line of its inferior surface a ridge {ib. fig. 2, n), which divides the external 

 nostrils anteriorly, and which rapidly expanding, as it descends, becomes continued into 

 the broad palatal plate of the premaxillary. The back part of the base of the septum 

 presents a triangular depression, on each side of the base of which is a canal, which 

 conducted vessels or nerves into the substance of the bone: the middle line of the 

 upper surface of the median branch of the premaxillary is impressed by a groove leading, 

 also, to a canal which enters the substance of the bone. Where this branch is confluent 

 with the body of the premaxillary, it slightly expands towards its anterior end, and a 

 deep and narrow groove divides it on each side from the body of the bone. This is 

 formed by a strong osseous mass curved downwards, with sharp lateral margins, and richly 

 perforated by vascular and nervous foramina. There is a slight median ridge along the 

 fore-part of the broad, moderately concave, palatal surface {ib. fig. 3) : and there is a broad 

 shallow channel along each side of the same surface, with numerous large foramina 

 opening into it. The outer border of this groove is sharply defined. Only the anterior 

 border of the naso-palatine foramen is here preserved ; a canal is continued forwards 

 from it into the substance of the bone. The apex of the massive, broad, deflected pre- 

 maxillary seems to have been rather obtuse. 



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