232 Annals of the Carnegie Museum. 



The rostrum is rounded beneath and carried to a distinct pointed 

 y)rocess anteriorly. Above this, as the anterior ethmoidal margin, it 

 is carried o]:)liquely forwards and upwards to finally spread out and 

 give support to the fore part of the cranium in the facial region, at its 

 inferior surface. 



Ibises lack basipterygoidal processes, and the pterygoids stand far 

 away from the lower part of the brain-case. 



A pterygoid is of good size, and may be said to be truly twisted upon 

 itself, with its hinder half very much compressed from side to side, as 

 is its anterior moiety similiarly compressed in the opposite direction. 

 Its anterior outer border is exceedingly sharp and thin. When the 

 pterygoids are articulated as in life, they make an extensive articulation 

 Avith pterygoidal heads of the palatines as they do with each other be- 

 neath the spheroidal rostrum. This is also the case in Tantalus, and 

 the bones are not altogether in the two genera. From side to side, 

 the palatines are very narrow bones. Posteriorly for a notably small 

 part of their extent they are tightly pressed together, and form on their 

 upper aspects in this locality a short longitudinal groove for the recep- 

 tion of the rostrum. In passing forwards they are quite parallel to 

 each other, and thus beneath the maxillo-palatines to become, in the 

 adult, completely and indistinguishably fused with the other bones. 

 Upon their under sides posteriorly, each one sends down both an in- 

 ternal and an external lamina of bone. These plates are about of equal 

 proportions, and the postero-external angle of the outer one is com- 

 pletely rounded off. Anteriorly, and upon their upper aspects, the 

 palatines develop extensive ascending processes or plates, which have 

 their planes nearly parallel to each other. These, when we regard the 

 skull upon its lateral aspect, shut the free part of the sphenoidal rostrum 

 out from view, and the entire anterior border of either one of them 

 has resting upon it, the large maxillo-palatine of the same side. Ple- 

 gadis, as in the case with other American Ibises, has a long, very 

 slender, and anteriorly pointed vomer. This bone is completely an- 

 chylosed with the palatines behind, exhibits barely any curvature as it 

 j)asses forwards, while its extreme tip just reaches the maxillo-palatines 

 at the point where those bones fuse across the interpalatine valley. 

 This vomer has only two points of contact then, and these are at its 

 extremities, it being nowhere else anywhere near the surrounding 

 bones. There is no doubt but that in very old Ibises the palatines 

 anchylose with each other in a very thorough manner. One specimen 



