172 



Anxals of thk Carnegik Museum. 



Fig. 5. Posterior view of the 

 skull of Ardea herodias. Man- 

 dible removed. Natural size. 

 By the author from the same 

 specimen as the others. 



This process forms a part of the lower margin of the vomer, which, as 

 I have said, it really is. The median plate of the vomer rises above 



this and extends beyond it, to jiroject 

 slightly into the interspace between the 

 maxillo-palatines. The upper margin of 

 this median vomerine plate is longitudin- 

 ally split, as it were, and the two thin 

 plates thus formed beautifully curl out- 

 wards and downwards, on either side, 

 creating as they do so a median longi- 

 tudinal groove on the upper aspect of 

 the vomer, over the hinder moiety of 

 which the apex of the rostrum hangs, 

 and even, still more posteriorly, meets 

 it in a free schindylesial articulation. 

 The middle third of the inner border of 

 the upper side of each palatine develops 

 a broad crest that curls outwards all along its summit. On lateral 

 view this crest hides the hinder half of the vomer. 



The maxillo-palatines of Anica herodias are of a highly spongy bone 

 tissue throughout. This material imperceptibly merges ' into the 

 more coarsely developed tissue of a similar character, which fills the 

 hollow of the superior mandible beyond. Laterally, the maxillo-pala- 

 tines may be said to spring from the anterior horizontal plates of the 

 maxillaries, on either side ; such a fact is only known to us though 

 from our knowledge of the development of these bones in other birds, 

 for we would hardly suspect it here. The hinder halves of these 

 bones rise parallel to each other, as lofty porous plates, which being 

 produced forwards meet the inner sides of the nasals and the premax- 

 illary to fiise with them. In Nycticorax these hinder moieties have a 

 thin outer layer of compact bone tissue covering them which more or 

 less masks their spongy nature. 



In this Heron the relations subsisting among the palatines, the 

 vomer, the rostrum of the sphenoid and the bones just described, 

 are about the same as we find them in Ardca. 



In both, too, we find that the median surfaces of the upper part of 

 the inner carination of the posterior third of the palatines are closely 

 applied to each other, so closely in fact that in dried skulls one has to 

 resort to the knife to separate them before we are assured that direct 



